Paglia D E, Valentine W N
Proc Natl Acad Sci U S A. 1981 Aug;78(8):5175-9. doi: 10.1073/pnas.78.8.5175.
Erythrocyte pyruvate kinase (PK) from a patient with PK deficiency was characterized according to internationally standardized procedures. In addition to low activity, the mutant isozyme displayed impaired kinetics specifically affecting the ADP-combining site:Km (ADP) was 3-5 times greater than normal when determined at three different concentrations of phosphoenolpyruvate (P-enolpyruvate). Maximum reaction velocities were not achieved until ADP was 10 times the concentration normally required for control PK. Substrate inhibition by high concentrations of ADP and competitive inhibition by ATP were markedly diminished. Other nucleoside diphosphates normally capable of replacing ADP in the PK reaction were less effective with the mutant isozyme than with PK from controls or from subjects with other forms of PK deficiency, and Michaelis--Menten constants for several of these (UDP, GDP, CDP) were significantly elevated. Whereas all previously known PK kinetic defects have involved the substrate P-enolpyruvate, the half-saturation constant K0.5s (P-enolpyruvate) for this mutant isozyme was normal, as was its response to fructose-1,6-bisphosphate activation.
根据国际标准化程序对一名丙酮酸激酶（PK）缺乏症患者的红细胞丙酮酸激酶进行了表征。除活性较低外，突变型同工酶的动力学受损，具体影响ADP结合位点：在三种不同浓度的磷酸烯醇丙酮酸（P-烯醇丙酮酸）下测定时，Km（ADP）比正常情况大3至5倍。直到ADP浓度达到对照PK正常所需浓度的10倍时，才达到最大反应速度。高浓度ADP的底物抑制和ATP的竞争性抑制明显减弱。其他通常能够在PK反应中替代ADP的核苷二磷酸对突变型同工酶的作用比对来自对照或患有其他形式PK缺乏症的受试者的PK的作用小，并且其中几种（UDP、GDP、CDP）的米氏常数显著升高。虽然所有先前已知的PK动力学缺陷都涉及底物P-烯醇丙酮酸，但这种突变型同工酶的半饱和常数K0.5s（P-烯醇丙酮酸）正常，其对果糖-1,6-二磷酸激活的反应也正常。
