β-aminoisobutyrate in the coupled enzymic assay of bovine lens γ-glutamylcysteine synthetase

✍ Scribed by William B. Rathbun; Howard D. Gilbert

• Book ID: 102628276
• Publisher: Elsevier Science
• Year: 1973
• Tongue: English
• Weight: 463 KB
• Volume: 54
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(73)90258-3

✦ Synopsis

The formation of ADP, a product of bovine lens y-glutamylcysteine synthetase activity, was determined by measurement of NADH oxidation in the pyruvate kinase-lactate dehydrogenase coupled assay system. Using a-aminobutyrate in place of cysteine, the time course of the spectrophotometric procedure was shown to be identical with the formation of ["CIlabeled dipeptide from tU"Cl-n-glutamate.

The assay for y-glutamylcysteine synthetase was used to demonstrate that /3-( + )-aminoisobutyrate was utilized at a rate two to three times that of the (-) isomer. The ability of the enzyme to distinguish between isomers suggests the binding site for the a-methyl group is a relatively broad area within the enzyme's active site.