Putman S J, Coulson A F, Farley I R, Riddleston B, Knowles J R
Biochem J. 1972 Sep;129(2):301-10. doi: 10.1042/bj1290301.
The isolation of crystalline triose phosphate isomerase from chicken breast muscle is described. The values of k(cat.) and K(m) for the reaction in each direction were determined from experiments over wide substrate-concentration ranges, and the reactions were shown to obey simple Michaelis-Menten kinetics. With d-glyceraldehyde 3-phosphate as substrate, k(cat.) is 2.56x10(5)min(-1) and K(m) is 0.47mm; with dihydroxyacetone phosphate as substrate, k(cat.) is 2.59x10(4)min(-1) and K(m) is 0.97mm. The enzyme-catalysed exchange of the methyl hydrogen atoms of the ;virtual substrate' monohydroxyacetone phosphate with solvent (2)H(2)O or (3)H(2)O was shown. This exchange is about 10(4)-fold slower than the corresponding exchange of the C-3 hydrogen of dihydroxyacetone phosphate. The other deoxy substrate, 3-hydroxypropionaldehyde phosphate, was synthesized, but is too unstable in aqueous solution for analogous proton-exchange reactions to be studied.
本文描述了从鸡胸肌中分离出结晶磷酸丙糖异构酶的过程。通过在较宽底物浓度范围内进行实验，测定了该酶在每个反应方向上的催化常数（k(cat.)）和米氏常数（K(m)），结果表明该反应遵循简单的米氏动力学。以d-甘油醛-3-磷酸为底物时，k(cat.)为2.56×10⁵ min⁻¹，K(m)为0.47 mM；以磷酸二羟丙酮为底物时，k(cat.)为2.59×10⁴ min⁻¹，K(m)为0.97 mM。实验还展示了该酶催化“虚拟底物”磷酸单羟基丙酮的甲基氢原子与溶剂(2)H₂O或(3)H₂O的交换。这种交换比磷酸二羟丙酮C-3位氢原子的相应交换慢约10⁴倍。另外还合成了另一种脱氧底物3-羟基丙醛磷酸，但它在水溶液中过于不稳定，无法用于研究类似的质子交换反应。
