Phosphorylation of Lactate Dehydrogenase by Protein Kinases

M. Yu. Yasykova, S. P. Petukhov, and V. I. Muronetz^*

Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (095) 939-3181; E-mail: vimuronets@beep.ru

^* To whom correspondence should be addressed.

Received February 21, 2000; Revision received March 30, 2000

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The influence of phosphorylation on the properties of lactate dehydrogenase (LDH) has been studied. Data obtained using the immobilization approach support the assumption that the autophosphorylation of LDH discovered previously in the presence of ATP has no relation to protein kinase activity of the enzyme. Phosphorylation of native LDH by tyrosine kinases was shown to be inefficient. However, the efficiency of the phosphorylation considerably increased after the dissociation of LDH into non-native forms of the enzyme. Ca²⁺/calmodulin-dependent protein kinase catalyzes incorporation of 0.8-0.9 mole phosphate per mole of LDH tetramer. The phosphorylation results in an increase in activity by 25-30% and increases markedly the stability of the enzyme during cold inactivation. Phosphorylation of LDH by Ca²⁺/calmodulin-dependent protein kinase, unlike the phosphorylation on tyrosine residues, is supposed to be of importance for the control of cell metabolism.

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KEY WORDS: phosphorylation, lactate dehydrogenase, protein kinase, tyrosine protein kinase, Ca²⁺/calmodulin-dependent protein kinase

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