Mechanism of Action of Rabbit Muscle Phosphoglucomutase

• Published in: The Journal of biological chemistry Vol. 249; no. 10; pp. 3166 - 3169
• Main Authors: Wålinder, Olov, Joshi, Jayant G.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 25.05.1974; American Society for Biochemistry and Molecular Biology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)42653-7

The rate of enzyme phosphate turnover of rabbit muscle phosphoglucomutase and the rate of glucose 1-phosphate turnover has been determined in a rapid mixing device both for the Mg2+ and the Zn2+-activated enzyme. In 1 µm glucose-1-P the turnover of enzyme phosphate of the Mg2+-activated enzyme was 5700 to 6700 min-1, while the rate of substrate phosphate turnover was 5900 min-1. The corresponding rates for the Zn2+-activated enzyme in 1 mm glucose-1-P were 20 to 30 min-1 and 10 min-1, respectively. Thus, in the presence of either metal, the enzyme phosphate was exchanged sufficiently rapidly to be a part of enzyme catalysis. Glucose 1,6-diphosphate did not alter the turnover rate of either the enzyme phosphate or the substrate phosphate for either of the two kinds of enzyme. This is in accord with the view that free glucose-1,6-P2 and dephosphoenzyme are not obligatory intermediates in the catalytic process.