ISSN:
1573-4919
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Medicine
Notes:
Summary 3-Hydroxykynureninase was purified from rat liver. The Michaelis constants for L-kynurenine and L-3-hydroxykynurenine were determined to be 2.33 × 10−4 m and 6.85 × 10−5 m, respectively, at pH 8.41 and 37°. With L-kynurenine as substrate, the enzyme was competitively inhibited by L-alanine, 3-hydroxyanthranilic acid, and several other compounds which contained structural features of either amino acid or aryl portions of the substrate. The effect of pH on the initial velocity, maximal velocity, and Michaelis constant, using L-kynurenine as substrate, was studied. Maximal velocity was strongly pH-dependent, with a maximum at pH 8.4. The Michaelis constant decreased from 11.4 × 10−4 m at pH 7.1 to 1.30 × 10−4 m at pH 9.0. Logarithmic plots of these data showed pKa's for functional groups ionizing in the enzyme-substrate complex and free enzyme active center of 7.6 and 8.5, respectively. Possible groups responsible for these ionizations were discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00280270
