Department of Bacteriology and Biochemistry, University of Idaho, Moscow, Idaho 83843.
Plant Physiol. 1983 May;72(1):194-9. doi: 10.1104/pp.72.1.194.
Glycine decarboxylase has been successfully solubilized from pea (Pisum sativum) leaf mitochondria as an acetone powder. The enzyme was dependent on added dithiothreitol and pyridoxal phosphate for maximal activity. The enzyme preparation could catalyze the exchange of CO(2) into the carboxyl carbon of glycine, the reverse of the glycine decarboxylase reaction by converting serine, NH(4) (+), and CO(2) into glycine, and (14)CO(2) release from [1-(14)C]glycine. The half-maximal concentrations for the glycine-bicarbonate exchange reaction were 1.7 millimolar glycine, 16 millimolar NaH(14)CO(2), and 0.006 millimolar pyridoxal phosphate. The enzyme (glycine-bicarbonate exchange reaction) was active in the assay conditions for 1 hour and could be stored for over 1 month. The enzymic mechanism appeared similar to that reported for the enzyme from animals and bacteria but some quantitative differences were noted. These included the tenacity of binding to the mitochondrial membrane, the concentration of pyridoxal phosphate needed for maximum activity, the requirement for dithiothreitol for maximum activity, and the total amount of activity present. Now that this enzyme has been solubilized, a more detailed understanding of this important step in photorespiration should be possible.
甘氨酸脱羧酶已成功地从豌豆（Pisum sativum）叶线粒体中以丙酮粉的形式溶解。该酶依赖于添加的二硫苏糖醇和吡哆醛磷酸以达到最大活性。该酶制剂可以催化 CO(2)与甘氨酸的羧基碳交换，这是甘氨酸脱羧酶反应的逆反应，通过将丝氨酸、NH(4) (+)和 CO(2)转化为甘氨酸，以及从[1-(14)C]甘氨酸中释放(14)CO(2)。甘氨酸-碳酸氢盐交换反应的半最大浓度为 1.7 毫摩尔甘氨酸、16 毫摩尔 NaH(14)CO(2)和 0.006 毫摩尔吡哆醛磷酸。该酶（甘氨酸-碳酸氢盐交换反应）在 1 小时的测定条件下具有活性，并且可以储存超过 1 个月。酶的机制似乎与动物和细菌中的酶报道的机制相似，但也注意到了一些定量差异。这些差异包括与线粒体膜的结合强度、达到最大活性所需的吡哆醛磷酸的浓度、达到最大活性所需的二硫苏糖醇以及存在的总活性量。既然这种酶已经被溶解，那么应该可以更详细地了解光合作用中这一重要步骤。
