The cleavage of pyrophosphate by human serum apo-transferrin
- Author:
Wei-Qing ZHONG
1
Author Information
1. Department of Inorganic Chemistry
- Publication Type:Journal Article
- From:
Academic Journal of Second Military Medical University
2006;27(1):71-75
- CountryChina
- Language:Chinese
-
Abstract:
Objective: To determine the rate constants for the cleavage of pyrophosphate to phosphate by human serum apotransferrin. Methods: The cleavage was followed by31P NMR spectroscopy. The data for concentration changes of pyrophosphate (as determined from its NMR peak intensity) with time, in the absence and the presence of MgCl2, at different pH values, were fitted to give second order rate constants. Results: The rate constnts at 312 K were 8.83×10-4 L · mmol-1 · h-1 at pH 6.85, 9.59×10-4 L · mmol-1 · h-1 at pH 7.4, and 1.38×10-3 L · mmol-1 · h-1 at pH 8.15, for reactions of apo-transferrin (0.5-1.0 mmol/L) with 5 molar equivalence of pyrophosphate. The rate constant increased to 1.21×10-3 L · mmol-1 · h-1 at pH 7.4,312 K when 2 mmol/L MgCl2 was added. Conclusion: The cleavage of pyrophosphate to phosphate by human serum apotransferrin is very slow and follows the second-order kinetics. Mg2+ can slightly enhance the rate of the cleavage.
