Anhydrides: Chemical compounds derived from acids by the elimination of a molecule of water.Phthalic Anhydrides: Phthalic acid anhydrides. Can be substituted on any carbon atom. Used extensively in industry and as a reagent in the acylation of amino- and hydroxyl groups.Maleic Anhydrides: Used in copolymerization reactions, in the Diels-Alder(diene)synthesis, in the preparation of resins, pharmaceuticals and agricultural chemicals. It is a powerful irritant and causes burns.Acid Anhydride Hydrolases: A group of enzymes that catalyze the hydrolysis of diphosphate bonds in compounds such as nucleoside di- and tri-phosphates, and sulfonyl-containing anhydrides such as adenylylsulfate. (Enzyme Nomenclature, 1992) EC 3.6.Succinic Anhydrides: A subclass of anhydrides with the general structure of dihydrofurandione. They can be substituted on any carbon atom. They modify and inhibit proteins and enzymes and are used in the acylation of amino- and hydroxyl groups.Acetic Anhydrides: Compounds used extensively as acetylation, oxidation and dehydrating agents and in the modification of proteins and enzymes.Aconitic AcidHydrolases: Any member of the class of enzymes that catalyze the cleavage of the substrate and the addition of water to the resulting molecules, e.g., ESTERASES, glycosidases (GLYCOSIDE HYDROLASES), lipases, NUCLEOTIDASES, peptidases (PEPTIDE HYDROLASES), and phosphatases (PHOSPHORIC MONOESTER HYDROLASES). EC 3.Respiration Disorders: Diseases of the respiratory system in general or unspecified or for a specific respiratory disease not available.Citraconic Anhydrides: Methylmaleic anhydrides.Occupational Exposure: The exposure to potentially harmful chemical, physical, or biological agents that occurs as a result of one's occupation.Occupational Diseases: Diseases caused by factors involved in one's employment.Glycoside Hydrolases