草蛇（游蛇科锦蛇属）肝脏中的黄嘌呤：烟酰胺腺嘌呤二核苷酸氧化还原酶

Xanthine:NAD+ oxidoreductase in the liver of grass snake Natrix natrix.

作者信息

Kamiński Z W

出版信息

Comp Biochem Physiol B. 1984;78(2):447-51. doi: 10.1016/0305-0491(84)90057-9.

Abstract

The enzyme hydroxylating oxypurines in the liver of grass snake (Natrix natrix, Colubridae) was found to be a stable xanthine:NAD+ oxidoreductase (EC 1.2.1.37). The Michaelis constants for NAD+ and xanthine amounted to 14.4 and 12.3 microM, respectively. The enzyme affinity to hypoxanthine is lower than that to xanthine, but the former substrate is hydroxylated faster than the latter. The enzyme is only slowly and slightly (up to 22%) inhibited by NADH accumulating during xanthine hydroxylation. The above data and the time-course of hypoxanthine----xanthine----uric acid hydroxylation indicated that the kinetic properties of the snake liver enzyme provide in this uricotelic animal fast elimination of superfluous nitrogen derived from protein catabolism.

摘要

在草蛇（游蛇科锦蛇属）肝脏中，能使氧嘌呤羟化的酶被发现是一种稳定的黄嘌呤：NAD⁺氧化还原酶（EC 1.2.1.37）。NAD⁺和黄嘌呤的米氏常数分别为14.4和12.3微摩尔。该酶对次黄嘌呤的亲和力低于对黄嘌呤的亲和力，但前者底物的羟化速度比后者快。在黄嘌呤羟化过程中积累的NADH对该酶仅有缓慢且轻微的抑制作用（最高达22%）。上述数据以及次黄嘌呤→黄嘌呤→尿酸羟化的时间进程表明，这种蛇肝脏酶的动力学特性使得这种排尿酸动物能够快速清除蛋白质分解代谢产生的多余氮。