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首页> 外文期刊>Biochemistry >Kinetic Characterization of Yeast Pyruvate Carboxylase Isozyme Pyc1 and the Pyc1 Mutant,C249A
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Kinetic Characterization of Yeast Pyruvate Carboxylase Isozyme Pyc1 and the Pyc1 Mutant,C249A

机译：酵母丙酮酸羧化酶同工酶Pyc1和Pyc1突变体C249A的动力学表征

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摘要

The yeast Pyc1 isoform of pyruvate carboxylasehas been further characterized and shown to differ form the Pyc2 isoform in its K~+ activation.Pyc1 differes from chicken liver pyruvate carboxylase in the lack of effect of acetyl-CoA on ADP phosphorylation by carbamoyl phosphate,which may be a result of differences in the loci of action of the effector between the two enzymes.Solvent D_2 O isotope effects have been measured with Pyc1 on the full pyruvatecarboxylation reaction,the ATPase reaction in the absence of pyruvate,and the carbamoyl phosphate-ADP phosphorylaton reaction for the first time for pyruvatecarboxylase.Proton inventories indicate that the measured isotope effects are due to a single proton transfer step in the reacton.The inverse to an active form.Kinetic measuremetns on the C249 A mutnt enzyme suggest that C249 is involved in the binding and action of enzyme activators K~+ and acetyl-CoA.C249 is not involved in ATP binding as was observed for the corresponding residue in the biotin carboxylase subunit fo Escherichia coli acetyl-CoA carbosxylase,nor is it directly responsible for the measured inverse ~D(K_cat/K_m) isotope effects.The size of the inverse sotope effects indicates that theymay result from formation of a low-barrier hydrogen bond.Modification of the wild type and C249A mutant with omicron-phthalaldehyde suggests that C249 is involved in isoindole formaiton but that the modification mutant with omicron-phthalaldehyde suggests that C249 is involved in isolindole formation but that the modification of this residue is not directly responsible for the accompanying major loss of enzyme activity.
机译：丙酮酸羧化酵母的酵母Pyc1同工型被进一步表征并显示出与Pyc2同工型的K〜+活化不同。Pyc1与鸡肝丙酮酸羧化酶的区别在于乙酰辅酶A对氨基甲酸酯磷酸对ADP磷酸化的影响不足。这是由于两种酶之间效应子的作用位点不同所致。用Pyc1测定了丙酮酸完全羧化反应，不存在丙酮酸的情况下ATPase反应和氨基甲酰磷酸-ADP磷酸化反应的溶剂D_2 O同位素效应。丙酮酸羧化酶的首次反应。质子清单表明，测得的同位素效应是由于反应中单个质子转移步骤所致。与活性形式相反.C249 A突变酶的动力学测量表明，C249参与了酶激活剂K〜+和乙酰辅酶A的结合和作用.C249不参与ATP的结合，因为在大肠杆菌乙酰辅酶A碳氧糖化酶的生物素羧化酶亚基，也不直接负责所测得的〜D（K_cat / K_m）同位素反作用。同位素反作用的大小表明它们可能是由于低势垒氢的形成用邻苯二甲醛修饰野生型和C249A突变体表明C249参与了异吲哚的形成，但经邻苯二甲醛修饰的突变表明C249参与了异吲哚的形成，但该残基的修饰并不直接引起对于伴随的酶活性的重大损失。

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