Scopes R K
Biochem J. 1973 May;134(1):197-208. doi: 10.1042/bj1340197.
A mixture of purified muscle glycolytic enzymes was reconstituted and the mixture shown to behave in a fashion analogous to that occurring in vivo. Glycolysis leads to ATP production in muscle and results in the phosphorylation of creatine. The extent of this phosphorylation by anaerobic glycolysis was shown to depend to a small extent on the relative proportions of available P(i) and creatine initially, but more importantly on the first step in glycolysis, in this case the enzyme phosphorylase. With less than 0.1% of the phosphorylase in the a form, only about one-third of the creatine was phosphorylated in 30min, whereas with 4% or more of phosphorylase a, 90% of the creatine was phosphorylated within this time. Inclusion of an adenosine triphosphatase decreased the steady-state concentration of phosphocreatine in the system. Calculations of the theoretical concentrations of ADP and AMP showed that phosphorylase b was almost inactive even in the presence of 9mum-AMP, because of ATP inhibition. With phosphorylase a present, glycolysis was able to continue at least until the calculated concentration of MgADP(-) was only 7mum, and AMP in the sub-mumolar range. The relation of these values to measured concentrations of nucleotides and to phosphorylase a percentages in intact muscle is discussed.
将纯化的肌肉糖酵解酶混合并重组，结果显示该混合物的行为方式与体内发生的情况类似。糖酵解导致肌肉中ATP的产生，并使肌酸磷酸化。厌氧糖酵解的磷酸化程度在一定程度上取决于最初可用的无机磷酸（P(i)）和肌酸的相对比例，但更重要的是取决于糖酵解的第一步，在这种情况下是磷酸化酶。当a型磷酸化酶含量低于0.1%时，在30分钟内只有约三分之一的肌酸被磷酸化，而当磷酸化酶a含量达到4%或更高时，在此时间段内90%的肌酸被磷酸化。加入三磷酸腺苷酶会降低系统中磷酸肌酸的稳态浓度。对ADP和AMP理论浓度的计算表明，即使存在9μM的AMP，磷酸化酶b几乎没有活性，这是由于ATP的抑制作用。当存在磷酸化酶a时，糖酵解至少能够持续到计算出的MgADP(-)浓度仅为7μM且AMP处于亚微摩尔范围内。讨论了这些值与完整肌肉中核苷酸测量浓度以及磷酸化酶a百分比的关系。
