Zhang Q, Wiskich J T
Department of Botany, University of Adelaide, Australia.
Arch Biochem Biophys. 1995 Jul 10;320(2):250-6. doi: 10.1016/0003-9861(95)90007-1.
Activity of glycine decarboxylase decreased by 60-70% after the isolated pea leaf mitochondria were aged for 5 h in the absence of glycine and was completely lost after 24 h. The reverse reaction, i.e., production of glycine from serine, ammonium, dihydrolipoate, and bicarbonate, was also inhibited in these aged mitochondria. Glycine decarboxylase could be reactivated by both exogenous and endogenous ATP. The latter was formed during the oxidation of succinate, malate, or oxoglutarate. Glycine decarboxylase consists of four subunits (P-, H-, L-, and T-proteins). The aged mitochondria were able to catalyze the exchange of [14C]-bicarbonate-glycine and the oxidation of dihydrolipoate, indicating the persistence of P-, H-, and L-protein activities. Serine hydroxymethyltransferase catalyzes the formation of serine from methylene tetrahydrofolate and another glycine and molecule at the last reaction of glycine oxidation. The aged mitochondria were able to catalyze the formation of methylene tetrahydrofolate from [14C]serine and its reverse reaction. Therefore, it was concluded that the loss of glycine decarboxylase activity was due to an inhibition of the reaction catalyzed by T-protein, which required ATP for its activation.
在无甘氨酸的情况下，分离的豌豆叶片线粒体老化5小时后，甘氨酸脱羧酶的活性降低了60% - 70%，24小时后则完全丧失。在这些老化的线粒体中，由丝氨酸、铵、二氢硫辛酸和碳酸氢盐生成甘氨酸的逆反应也受到抑制。甘氨酸脱羧酶可被外源性和内源性ATP重新激活。后者是在琥珀酸、苹果酸或酮戊二酸氧化过程中形成的。甘氨酸脱羧酶由四个亚基（P-、H-、L-和T-蛋白）组成。老化的线粒体能够催化[14C] - 碳酸氢盐 - 甘氨酸的交换以及二氢硫辛酸的氧化，这表明P-、H-和L-蛋白的活性仍然存在。丝氨酸羟甲基转移酶在甘氨酸氧化的最后一步反应中，催化由亚甲基四氢叶酸和另一个甘氨酸分子生成丝氨酸。老化的线粒体能够催化由[14C]丝氨酸生成亚甲基四氢叶酸及其逆反应。因此，得出的结论是，甘氨酸脱羧酶活性的丧失是由于T-蛋白催化的反应受到抑制，而该反应需要ATP来激活。
