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Phosphorylation by liver glucokinase of D ‐glucose anomers at anomeric equilibrium
Author(s) -
Zähner Dagmar,
Malaisse Willy J.
Publication year - 1991
Publication title -
cell biochemistry and function
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.933
H-Index - 61
eISSN - 1099-0844
pISSN - 0263-6484
DOI - 10.1002/cbf.290090108
Subject(s) - glucokinase , anomer , hexokinase , chemistry , glycogen phosphorylase , biochemistry , glycogen , enzyme , glycolysis
The relative contribution of each anomer of D‐glucose to the overall phosphorylation rate of the hexose tested at anomeric equilibrium was examined in rat liver postmicrosomal supernatants under conditions aimed at characterizing the activity of glucokinase, with negligible interference of either hexokinase, N ‐acetyl‐ D ‐glucosamine kinase or glucose‐6‐phosphatase (acting as a phosphotransferase). Both at 10° and 30°C, the relative contribution of each anomer was unaffected by the concentration of D ‐glucose. At both temperatures, the α/β ratio for the contribution of each anomer was slightly, but significantly, lower than the α/β ratio of anomer concentrations. These findings, which are consistent with the anomeric specificity of glucokinase in terms of affinity, cooperativity and maximal velocity, reveal that the preferred α‐anomeric substrate for both glycogen synthesis and glycolysis is generated by glucokinase at a lower rate than is β‐ D ‐glucose‐6‐phosphate.