Marechal L R, Oliver G, Veiga L A, de Ruiz Holgado A A
Arch Biochem Biophys. 1984 Feb 1;228(2):592-9. doi: 10.1016/0003-9861(84)90027-4.
A phosphoglucomutase (beta-phosphoglucomutase) specific for beta-glucose 1-phosphate, which catalyzes the beta-glucose 1-phosphate:glucose 6-phosphate interconversion, was 560-fold purified from Lactobacillus brevis strain L6. The isoelectric point of beta-phosphoglucomutase was 3.8 and it had an apparent molecular weight of 29,000 estimated by gel chromatography. The enzyme required a divalent cation (Mn2+ greater than Mg2+ greater than Ni2+ greater than Co2+) and beta-glucose 1,6-bisphosphate for activity. The equilibrium constant Ke for the reaction beta-D-glucose 1-phosphate in equilibrium D-glucose 6-phosphate at 30 degrees C and pH 6.7 is 18.5. beta-phosphoglucomutase had a pH optimum between 6.3 and 6.8 and appeared to be quite specific: alpha-glucose 1-phosphate, alpha- or beta-galactose 1-phosphate and alpha- or beta-N-acetylglucosamine 1-phosphate did not substitute for beta-glucose 1-phosphate. Double reciprocal plots of the data from initial velocity studies at five beta-glucose 1-phosphate concentrations (10 to 100 microM) and four beta-glucose 1,6-bisphosphate concentrations (0.125 to 1.0 microM) showed that the apparent Michaelis constants for beta-glucose 1-phosphate and beta-glucose 1,6-bisphosphate were related to the concentrations of beta-glucose 1,6-bisphosphate and beta-glucose 1-phosphate, respectively, in such a way as to suggest a ping-pong mechanism. The same conclusion was obtained when substrate-velocity relationships were investigated at fixed ratio of both substrates: the Lineweaver-Burk plots showed linear lines and no parabolic ones. The "true" Km for beta-glucose 1-phosphate and beta-glucose 1,6-bisphosphate were found to be about 12 and 0.8 microM, respectively.
一种对β-葡萄糖1-磷酸具有特异性的磷酸葡萄糖变位酶（β-磷酸葡萄糖变位酶），它催化β-葡萄糖1-磷酸与葡萄糖6-磷酸之间的相互转化，该酶从短乳杆菌L6菌株中经过560倍纯化得到。β-磷酸葡萄糖变位酶的等电点为3.8，通过凝胶色谱法估算其表观分子量为29,000。该酶活性需要二价阳离子（Mn2+＞Mg2+＞Ni2+＞Co2+）和β-葡萄糖1,6-二磷酸。在30℃和pH 6.7条件下，β-D-葡萄糖1-磷酸与D-葡萄糖6-磷酸反应的平衡常数Ke为18.5。β-磷酸葡萄糖变位酶的最适pH在6.3至6.8之间，并且似乎具有很高的特异性：α-葡萄糖1-磷酸、α-或β-半乳糖1-磷酸以及α-或β-N-乙酰葡糖胺1-磷酸均不能替代β-葡萄糖1-磷酸。在五个β-葡萄糖1-磷酸浓度（10至100μM）和四个β-葡萄糖1,6-二磷酸浓度（0.125至1.0μM）下进行的初始速度研究数据的双倒数作图表明，β-葡萄糖1-磷酸和β-葡萄糖1,6-二磷酸的表观米氏常数分别与β-葡萄糖1,6-二磷酸和β-葡萄糖1-磷酸的浓度相关，这表明存在乒乓机制。当以两种底物的固定比例研究底物-速度关系时，也得到了相同的结论：Lineweaver-Burk作图显示为直线而非抛物线。发现β-葡萄糖1-磷酸和β-葡萄糖1,6-二磷酸的“真实”Km分别约为12μM和0.8μM。
