S-aminopropylcysteine and S-aminoethylhomocysteine are oxidized by snake venom L-amino acid oxidase in the presence of catalase with formation of the respective ketoderivatives. Only the ketoderivative of S-aminopropylcysteine cyclizes to give a seven membered ring (ketimine) absorbing at 296 nm. In the absence of catalase both ketoderivatives are oxidatively decarboxylated.

Amines↗

PubMedDate not supplied

Influence of diet on cystathionine ketimine and lanthionine ketimine content in human urine.

A simple HPLC procedure for the routine analyses of Cystathionine ketimine (CK) and Lanthionine ketimine (LK) content in human urine has been developed. The values obtained in morning urine of fifteen healthy subjects (both sexes, 25-45 years old) on a common mixed diet are 330-2480 micrograms/g creatinine (mean 1110) of CK and 100-420 micrograms/g creatinine (mean 200) of LK. Quantitation of the two ketimines in urine of subjects on strictly vegetarian diet indicate that while the excretion of LK is independent of the diet, the excretion of CK is significantly decreased in conditions of vegetarian diet.

Adult↗

PubMedDate not supplied

Crystalline rhodanese from beef kidney.

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Ammonium Sulfate↗

PubMedDate not supplied

Studies of cyanolysis of the rhodanese-thionitrobenzoate complex.

The reaction of sulfur-free rhodanese with 5-5'-dithio-bis (2-nitrobenzoic acid) produces a modified enzyme with 35% of residual activity. The resulting enzyme derivative has 1.6 moles of thionitrobenzoate/mole of enzyme bound to sulfhydryl groups of rhodanese. Determination of free sulfhydryl groups of this derivative shows that during the reaction with 5-5'-dithio-bis (2-nitrobenzoic acid) oxidative formation of an intramolecular disulfide bridge between two sulfhydryl groups of rhodanese occurs. Cyanolysis of the modified enzyme produces an enzyme-thiocyano derivative which partially beta-eliminates with release of thiocyanate. The cleavage of disulfide bonds present in the enzyme-thionitrobenzoate adduct using labeled cyanide shows an incorporation of radioactivity in the protein higher than would be expected. An electrostatic bond between cyanide and positively charged groups of the enzyme is suggested. Most of bound cyanide is released when samples are acidified for protein hydrolysis. In these conditions the thiocyanoalanine residue cyclizes to form 2-iminothiazolidine-4-carboxylic acid.

Animals↗