Norleucine: An unnatural amino acid that is used experimentally to study protein structure and function. It is structurally similar to METHIONINE, however it does not contain SULFUR.Acremonium: A mitosporic fungal genus with many reported ascomycetous teleomorphs. Cephalosporin antibiotics are derived from this genus.HomoarginineLeucine: An essential branched-chain amino acid important for hemoglobin formation.Methionine: A sulfur-containing essential L-amino acid that is important in many body functions.Valine: A branched-chain essential amino acid that has stimulant activity. It promotes muscle growth and tissue repair. It is a precursor in the penicillin biosynthetic pathway.Isoleucine: An essential branched-chain aliphatic amino acid found in many proteins. It is an isomer of LEUCINE. It is important in hemoglobin synthesis and regulation of blood sugar and energy levels.Ethionine: 2-Amino-4-(ethylthio)butyric acid. An antimetabolite and methionine antagonist that interferes with amino acid incorporation into proteins and with cellular ATP utilization. It also produces liver neoplasms.Amino Acids: Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.