Effect of lithium salts on lactate dehydrogenase, adenylate kinase, and 1-phosphofructokinase activities

Abstract

Inhibitions of 30 nM rabbit muscle 1-phosphofructokinase (PFK-1) by lithium, potassium, and sodium salts showed inhibition or not depending upon the anion present. Generally, potassium salts were more potent inhibitors than sodium salts; the extent of inhibition by lithium salts also varied with the anion. Li₂CO₃ was a relatively potent inhibitor of PFK-1 but LiCl and lithium acetate were not. Our results suggest that extents of inhibition by monovalent salts were due to both cations and anions, and the latter needs to be considered before inhibition can be credited to the cation. An explanation for monovalent salt inhibitions is proffered involving interactions of both cations and anions at negative and positive sites of PFK-1 that affect enzyme activity. Our studies suggest that lithium cations per se are not inhibitors: the inhibitors are the lithium salts, and we suggest that in vitro studies involving the effects of monovalent salts on enzymes should involve more than one anion.

Keywords::

• PFK-1
• lithium salts
• inhibitions
• anions
• aldolase

Acknowledgments

The project/study described was partially supported by Grant Number P60 MD00220 from the San Diego EXPORT, NCMHD, NIH; by Grant Number 1 R25 GM73590 from the UCSD CURE Program, National Cancer Institute, NIH; and by Grant Number R25 GM083275 UCSD IMSD Program National Institute of General Medical Sciences, NIH. The contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health.