Guanosine triphosphate cyclohydrolase activity in rat tissues.
Guanosine triphosphate cyclohydrolase activity in rat tissues.
复制标题
大鼠组织中三磷酸鸟苷环水解酶活性。
DOI：
10.1042/bj2170059
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发表时间：
1984
期刊：
影响因子：
--
通讯作者：
J. Farriaux
中科院分区：
文献类型：
--
作者：
Z. Bellahsene;J. Dhondt;J. Farriaux
The GTP cyclohydrolase activity of rat tissues has been studied by means of the measurement of formic acid release and neopterin synthesis from GTP. After gel filtration of a 45%-satd.-(NH4)2SO4 fraction of liver homogenates, three enzyme fractions were separated and named A1, A2 and A3 according to the order of their elution. Fractions A1 and A3 displayed an 8-formyl-GTP deformylase activity; no proof of cyclized product has yet been established. This activity was heat-labile and required Mg2+ for maximal activity. Fraction A2 displayed a 'neopterin-synthetase' activity, with dihydroneopterin triphosphate and formic acid formed in stochiometric amounts. Fraction A1 isolated from heat-treated homogenates also produced dihydroneopterin triphosphate. Neopterin synthetase activity in fractions A1 and A2 was heat-resistant and inhibited by Mg2+. In liver the A2 fraction represented 70-75% of the neopterin synthetase capacity and was inhibited by reduced pterines (sepiapterin, dihydrobiopterin and tetrahydrobiopterin) and to a lesser extent by reduced forms of folic acid. In kidney and brain, fraction A1 and A3 GTP 8-formylhydrolase activities were found in significant amounts, in contrast with the neopterin synthetase activity, which was low and appeared to be confined to the A1 fraction.
