Department of Food Science and Technology, University of California, Davis, California 95616.
Plant Physiol. 1975 Mar;55(3):502-6. doi: 10.1104/pp.55.3.502.
2-oxoacid aminotransferase (EC 2.6.1.13) has been purified over 400-fold with a total recovery of 14% from acetone powders of cotyledons of germinating squash (Cucurbita pepo, L.) seedlings. The pH optimum of the transamination between l-ornithine and alpha-ketoglutarate is 8 and the Michaelis constants are 4.7 mm and 6.3 mm, respectively. The enzyme has a molecular weight of 48,000 as determined by gel filtration. The reaction is essentially specific for alpha-ketoglutarate as the amino group acceptor. The enzyme is inhibited very strongly by hydroxylamine, and less severely by NaCN and isonicotinylhydrazide. No inhibition is observed in the presence of 10 mml-cysteine. The energy of activation is 7.6 kcal/mole. The stability of the enzyme preparation is enhanced by the presence of dithioerythritol and glycerol. The enzyme activity of the most purified fraction is stimulated 30% by the addition of pyridoxal phosphate; however, the evidence for the unequivocal involvement of pyridoxal phosphate was inconclusive.
2-氧代酸氨基转移酶（EC 2.6.1.13）已从萌发南瓜（Cucurbita pepo，L.）幼苗子叶的丙酮粉中得到 400 倍以上的纯化，总回收率为 14%。鸟氨酸和α-酮戊二酸之间转氨基的 pH 最佳值为 8，米氏常数分别为 4.7mm 和 6.3mm。该酶通过凝胶过滤确定分子量为 48,000。该酶基本上特异性地以α-酮戊二酸作为氨基受体。羟胺强烈抑制该酶，氰化钠和异烟酰肼抑制作用较弱。存在 10 mml-半胱氨酸时，未观察到抑制作用。该酶的激活能为 7.6kcal/mol。二硫苏糖醇和甘油的存在增强了酶制剂的稳定性。最纯化的部分的酶活性通过添加吡哆醛磷酸盐水解酶刺激 30%；然而，吡哆醛磷酸盐水解酶的明确参与的证据尚无定论。
