Calcium
A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.
Phospholipases
A class of enzymes that catalyze the hydrolysis of phosphoglycerides or glycerophosphatidates. EC 3.1.-.
Phospholipases A
Phospholipases A2
Phospholipases A1
Group II Phospholipases A2
A subcategory of secreted phospholipases A2 that includes enzymes isolated from a variety of sources. The creation of this group is based upon similarities in the structural determinants of the enzymes including a negatively charged carboxy-terminal segment.
Type C Phospholipases
A subclass of phospholipases that hydrolyze the phosphoester bond found in the third position of GLYCEROPHOSPHOLIPIDS. Although the singular term phospholipase C specifically refers to an enzyme that catalyzes the hydrolysis of PHOSPHATIDYLCHOLINE (EC 3.1.4.3), it is commonly used in the literature to refer to broad variety of enzymes that specifically catalyze the hydrolysis of PHOSPHATIDYLINOSITOLS.
Calcium Signaling
Signal transduction mechanisms whereby calcium mobilization (from outside the cell or from intracellular storage pools) to the cytoplasm is triggered by external stimuli. Calcium signals are often seen to propagate as waves, oscillations, spikes, sparks, or puffs. The calcium acts as an intracellular messenger by activating calcium-responsive proteins.
Group X Phospholipases A2
A secreted phospholipase A2 subtype that contains a interfacial-binding region with specificity for PHOSPHATIDYLCHOLINE. This enzyme group may play a role in eliciting ARACHIDONIC ACID release from intact cellular membranes and from LOW DENSITY LIPOPROTEINS. Members of this group bind specifically to PHOSPHOLIPASE A2 RECEPTORS.
Phospholipases A2, Secretory
A subcategory of phospholipases A2 that are secreted from cells. They are 14 kDa proteins containing multiple disulfide-bonds and access their substrate via an interfacial binding site that interacts with phospholipid membranes. In addition specific PHOSPHOLIPASE A2 RECEPTORS can bind to and internalize the enzymes.
Group I Phospholipases A2
A subcategory of secreted phospholipases A2 that includes enzymes isolated from ELAPID VENOMS and pancreatic sources. The creation of this group is based upon similarities in the structural determinants of the enzymes.
Lysophospholipase
An enzyme that catalyzes the hydrolysis of a single fatty acid ester bond in lysoglycerophosphatidates with the formation of glyceryl phosphatidates and a fatty acid. EC 3.1.1.5.
Calcium Channels
Voltage-dependent cell membrane glycoproteins selectively permeable to calcium ions. They are categorized as L-, T-, N-, P-, Q-, and R-types based on the activation and inactivation kinetics, ion specificity, and sensitivity to drugs and toxins. The L- and T-types are present throughout the cardiovascular and central nervous systems and the N-, P-, Q-, & R-types are located in neuronal tissue.
Group V Phospholipases A2
A subcategory of secreted phospholipases A2 that contains both a negatively charged carboxy-terminal segment and interfacial-binding region specific for PHOSPHATIDYL CHOLINE-containing membranes. This enzyme group may play a role in the release of ARACHIDONIC ACID from phospholipid membranes.
Calcium, Dietary
Snake Venoms
Phospholipase D
Crotalid Venoms
Venoms from snakes of the subfamily Crotalinae or pit vipers, found mostly in the Americas. They include the rattlesnake, cottonmouth, fer-de-lance, bushmaster, and American copperhead. Their venoms contain nontoxic proteins, cardio-, hemo-, cyto-, and neurotoxins, and many enzymes, especially phospholipases A. Many of the toxins have been characterized.
Group VI Phospholipases A2
Receptors, Phospholipase A2
Cell surface receptors that bind to and internalize SECRETED PHOSPHOLIPASES A2. Although primarily acting as scavenger receptors, these proteins may also play a role in intracellular signaling. Soluble forms of phospholipase A2 receptors occur through the action of proteases and may a play a role in the inhibition of extracellular phospholipase activity.
Cobra Venoms
Venoms from snakes of the genus Naja (family Elapidae). They contain many specific proteins that have cytotoxic, hemolytic, neurotoxic, and other properties. Like other elapid venoms, they are rich in enzymes. They include cobramines and cobralysins.
Group IV Phospholipases A2
A cytosolic phospholipase A2 group that plays an important role in the release of free ARACHIDONIC ACID, which in turn is metabolized to PROSTAGLANDINS by the CYCLOOXYGENASE pathway and to LEUKOTRIENES by the 5-LIPOXYGENASE pathway.
Viperidae
A family of snakes comprising three subfamilies: Azemiopinae (the mountain viper, the sole member of this subfamily), Viperinae (true vipers), and Crotalinae (pit vipers). They are widespread throughout the world, being found in the United States, Central and South America, Europe, Asia and Africa. Their venoms act on the blood (hemotoxic) as compared to the venom of elapids which act on the nervous system (neurotoxic). (Goin, Goin, and Zug, Introduction to Herpetology, 3d ed, pp333-36)
Bothrops
Calcium Carbonate
Phospholipids
Lipids containing one or more phosphate groups, particularly those derived from either glycerol (phosphoglycerides see GLYCEROPHOSPHOLIPIDS) or sphingosine (SPHINGOLIPIDS). They are polar lipids that are of great importance for the structure and function of cell membranes and are the most abundant of membrane lipids, although not stored in large amounts in the system.
Viper Venoms
Venoms from SNAKES of the viperid family. They tend to be less toxic than elapid or hydrophid venoms and act mainly on the vascular system, interfering with coagulation and capillary membrane integrity and are highly cytotoxic. They contain large amounts of several enzymes, other factors, and some toxins.
Crotoxin
A specific complex of toxic proteins from the venom of Crotalus durissus terrificus (South American rattlesnake). It can be separated into a phospholipase A and crotapotin fragment; the latter consists of three different amino acid chains, potentiates the enzyme, and is specifically neurotoxic.
Calcium Phosphates
Calcium salts of phosphoric acid. These compounds are frequently used as calcium supplements.
Group III Phospholipases A2
A subcategory of secreted phospholipases A2 with specificity for PHOSPHATIDYLETHANOLAMINES and PHOSPHATIDYLCHOLINE. It occurs as a component of VENOMS and as a mammalian secretory phospholipase A2. The creation of this group is based upon similarities in the structural determinants of the enzymes including a long amino-terminal domain, a conserved group III-specific domain, and a long carboxyl-terminal domain.
Calcium Isotopes
Stable calcium atoms that have the same atomic number as the element calcium, but differ in atomic weight. Ca-42-44, 46, and 48 are stable calcium isotopes.
Elapid Venoms
Venoms from snakes of the family Elapidae, including cobras, kraits, mambas, coral, tiger, and Australian snakes. The venoms contain polypeptide toxins of various kinds, cytolytic, hemolytic, and neurotoxic factors, but fewer enzymes than viper or crotalid venoms. Many of the toxins have been characterized.
Arachidonic Acid
An unsaturated, essential fatty acid. It is found in animal and human fat as well as in the liver, brain, and glandular organs, and is a constituent of animal phosphatides. It is formed by the synthesis from dietary linoleic acid and is a precursor in the biosynthesis of prostaglandins, thromboxanes, and leukotrienes.
Phosphatidylcholines
Derivatives of phosphatidic acids in which the phosphoric acid is bound in ester linkage to a choline moiety. Complete hydrolysis yields 1 mole of glycerol, phosphoric acid and choline and 2 moles of fatty acids.
Calcium Chloride
A salt used to replenish calcium levels, as an acid-producing diuretic, and as an antidote for magnesium poisoning.
Elapidae
A family of extremely venomous snakes, comprising coral snakes, cobras, mambas, kraits, and sea snakes. They are widely distributed, being found in the southern United States, South America, Africa, southern Asia, Australia, and the Pacific Islands. The elapids include three subfamilies: Elapinae, Hydrophiinae, and Lauticaudinae. Like the viperids, they have venom fangs in the front part of the upper jaw. The mambas of Africa are the most dangerous of all snakes by virtue of their size, speed, and highly toxic venom. (Goin, Goin, and Zug, Introduction to Herpetology, 3d ed, p329-33)
Phospholipases A2, Calcium-Independent
Phospholipases A2, Cytosolic
Bee Venoms
Calcium Channels, L-Type
Long-lasting voltage-gated CALCIUM CHANNELS found in both excitable and nonexcitable tissue. They are responsible for normal myocardial and vascular smooth muscle contractility. Five subunits (alpha-1, alpha-2, beta, gamma, and delta) make up the L-type channel. The alpha-1 subunit is the binding site for calcium-based antagonists. Dihydropyridine-based calcium antagonists are used as markers for these binding sites.
Phosphatidylinositols
Derivatives of phosphatidic acids in which the phosphoric acid is bound in ester linkage to the hexahydroxy alcohol, myo-inositol. Complete hydrolysis yields 1 mole of glycerol, phosphoric acid, myo-inositol, and 2 moles of fatty acids.
Amino Acid Sequence
Calcium Oxalate
The calcium salt of oxalic acid, occurring in the urine as crystals and in certain calculi.
Group IA Phospholipases A2
Phospholipase A2 Inhibitors
Cytosol
Calcium Gluconate
Phosphatidylinositol Diacylglycerol-Lyase
A phosphorus-oxygen lyase found primarily in BACTERIA. The enzyme catalyzes the cleavage of a phosphoester linkage in 1-phosphatidyl-1D-myo-inositol to form 1D-myo-inositol 1,2-cyclic phosphate and diacylglycerol. The enzyme was formerly classified as a phosphoric diester hydrolase (EC 3.1.4.10) and is often referred to as a TYPE C PHOSPHOLIPASES. However it is now known that a cyclic phosphate is the final product of this enzyme and that water does not enter into the reaction.
Molecular Sequence Data
Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.
Isoenzymes
Calcium Radioisotopes
Unstable isotopes of calcium that decay or disintegrate emitting radiation. Ca atoms with atomic weights 39, 41, 45, 47, 49, and 50 are radioactive calcium isotopes.
Egtazic Acid
Phosphatidic Acids
Calcimycin
An ionophorous, polyether antibiotic from Streptomyces chartreusensis. It binds and transports CALCIUM and other divalent cations across membranes and uncouples oxidative phosphorylation while inhibiting ATPase of rat liver mitochondria. The substance is used mostly as a biochemical tool to study the role of divalent cations in various biological systems.
Hydrogen-Ion Concentration
Enzyme Activation
Pancreas
A nodular organ in the ABDOMEN that contains a mixture of ENDOCRINE GLANDS and EXOCRINE GLANDS. The small endocrine portion consists of the ISLETS OF LANGERHANS secreting a number of hormones into the blood stream. The large exocrine portion (EXOCRINE PANCREAS) is a compound acinar gland that secretes several digestive enzymes into the pancreatic ductal system that empties into the DUODENUM.
Substrate Specificity
Cells, Cultured
Phosphatidylethanolamines
Derivatives of phosphatidic acids in which the phosphoric acid is bound in ester linkage to an ethanolamine moiety. Complete hydrolysis yields 1 mole of glycerol, phosphoric acid and ethanolamine and 2 moles of fatty acids.
Bacillus cereus
Crotalus
A genus of snakes of the family VIPERIDAE, one of the pit vipers, so-called from the pit hollowing out the maxillary bone, opening between the eye and the nostril. They are distinctively American serpents. Most of the 25 recognized species are found in the southwestern United States and northern Mexico. Several species are found as far north as Canada and east of the Mississippi, including southern Appalachia. They are named for the jointed rattle (Greek krotalon) at the tip of their tail. (Goin, Goin, and Zug: Introduction to Herpetology, 3d ed; Moore: Poisonous Snakes of the World, 1980, p335)
Arachidonic Acids
Arachidonic acids are polyunsaturated fatty acids, specifically a type of omega-6 fatty acid, that are essential for human nutrition and play crucial roles in various biological processes, including inflammation, immunity, and cell signaling. They serve as precursors to eicosanoids, which are hormone-like substances that mediate a wide range of physiological responses.
Diglycerides
Quinacrine
Calcium Compounds
Inorganic compounds that contain calcium as an integral part of the molecule.
Membrane Lipids
Lipids, predominantly phospholipids, cholesterol and small amounts of glycolipids found in membranes including cellular and intracellular membranes. These lipids may be arranged in bilayers in the membranes with integral proteins between the layers and peripheral proteins attached to the outside. Membrane lipids are required for active transport, several enzymatic activities and membrane formation.
Phosphoinositide Phospholipase C
A type C phospholipase with specificity towards PHOSPHATIDYLINOSITOLS that contain INOSITOL 1,4,5-TRISPHOSPHATE. Many of the enzymes listed under this classification are involved in intracellular signaling.
Calcium Channels, N-Type
Lysophosphatidylcholines
Derivatives of PHOSPHATIDYLCHOLINES obtained by their partial hydrolysis which removes one of the fatty acid moieties.
Trimeresurus
A genus of snakes of the family VIPERIDAE. About 30 species are currently recognized, found in southeast Asia and adjacent island chains. The Okinawa habu frequently enters dwellings in search of rats and mice; the Chinese habu is often found in suburban and agricultural areas. They are quite irritable. (Moore: Poisonous Snakes of the World, 1980, p136)
Signal Transduction
The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway.
Group IB Phospholipases A2
A subclass of group I phospholipases A2 that includes enzymes isolated from PANCREATIC JUICE. Members of this group have specificity for PHOSPHOLIPASE A2 RECEPTORS.
Thiones
Calcium Channel Agonists
Agents that increase calcium influx into calcium channels of excitable tissues. This causes vasoconstriction in VASCULAR SMOOTH MUSCLE and/or CARDIAC MUSCLE cells as well as stimulation of insulin release from pancreatic islets. Therefore, tissue-selective calcium agonists have the potential to combat cardiac failure and endocrinological disorders. They have been used primarily in experimental studies in cell and tissue culture.
Russell's Viper
A genus of snakes of the family VIPERIDAE. It is distributed in West Pakistan, most of India, Burma, Ceylon, Thailand, southeast China, Taiwan, and a few islands of Indonesia. It hisses loudly when disturbed and strikes with great force and speed. Very prolific, it gives birth to 20-60 young. This viper is the leading cause of snakebite in India and Burma. (Moore: Poisonous Snakes of the World, 1980, p127)
Glycerophospholipids
Derivatives of phosphatidic acid in which the hydrophobic regions are composed of two fatty acids and a polar alcohol is joined to the C-3 position of glycerol through a phosphodiester bond. They are named according to their polar head groups, such as phosphatidylcholine and phosphatidylethanolamine.
Enzyme Inhibitors
Phospholipase C beta
A phosphoinositide phospholipase C subtype that is primarily regulated by its association with HETEROTRIMERIC G-PROTEINS. It is structurally related to PHOSPHOLIPASE C DELTA with the addition of C-terminal extension of 400 residues.
Micelles
Particles consisting of aggregates of molecules held loosely together by secondary bonds. The surface of micelles are usually comprised of amphiphatic compounds that are oriented in a way that minimizes the energy of interaction between the micelle and its environment. Liquids that contain large numbers of suspended micelles are referred to as EMULSIONS.
Rabbits
Lysophospholipids
Derivatives of PHOSPHATIDIC ACIDS that lack one of its fatty acyl chains due to its hydrolytic removal.
Edetic Acid
A chelating agent that sequesters a variety of polyvalent cations such as CALCIUM. It is used in pharmaceutical manufacturing and as a food additive.
Indolizidines
Swine
Any of various animals that constitute the family Suidae and comprise stout-bodied, short-legged omnivorous mammals with thick skin, usually covered with coarse bristles, a rather long mobile snout, and small tail. Included are the genera Babyrousa, Phacochoerus (wart hogs), and Sus, the latter containing the domestic pig (see SUS SCROFA).
Lysosomes
A class of morphologically heterogeneous cytoplasmic particles in animal and plant tissues characterized by their content of hydrolytic enzymes and the structure-linked latency of these enzymes. The intracellular functions of lysosomes depend on their lytic potential. The single unit membrane of the lysosome acts as a barrier between the enzymes enclosed in the lysosome and the external substrate. The activity of the enzymes contained in lysosomes is limited or nil unless the vesicle in which they are enclosed is ruptured. Such rupture is supposed to be under metabolic (hormonal) control. (From Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed)
Dose-Response Relationship, Drug
Calcium Hydroxide
Neomycin
Phosphorus
Clostridium perfringens
Eicosanoids
Cattle
Nifedipine
A potent vasodilator agent with calcium antagonistic action. It is a useful anti-anginal agent that also lowers blood pressure.
Calcium Sulfate
A calcium salt that is used for a variety of purposes including: building materials, as a desiccant, in dentistry as an impression material, cast, or die, and in medicine for immobilizing casts and as a tablet excipient. It exists in various forms and states of hydration. Plaster of Paris is a mixture of powdered and heat-treated gypsum.
Cell Membrane
Binding Sites
Parathyroid Hormone
A polypeptide hormone (84 amino acid residues) secreted by the PARATHYROID GLANDS which performs the essential role of maintaining intracellular CALCIUM levels in the body. Parathyroid hormone increases intracellular calcium by promoting the release of CALCIUM from BONE, increases the intestinal absorption of calcium, increases the renal tubular reabsorption of calcium, and increases the renal excretion of phosphates.
Glycosylphosphatidylinositols
Compounds containing carbohydrate or glycosyl groups linked to phosphatidylinositols. They anchor GPI-LINKED PROTEINS or polysaccharides to cell membranes.