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Biophys J. 1998 May;74(5):2658-65.

Time-dependent effects of trimethylamine-N-oxide/urea on lactate dehydrogenase activity: an unexplored dimension of the adaptation paradigm.

Author information

1
Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston 77555-1052, USA.

Abstract

Given that enzymes in urea-rich cells are believed to be just as sensitive to urea effects as enzymes in non-urea-rich cells, it is argued that time-dependent inactivation of enzymes by urea could become a factor of overriding importance in the biology of urea-rich cells. Time-independent parameters (e.g. Tm, k(cat), and Km) involving protein stability and enzyme function have generally been the focus of inquiries into the efficacy of naturally occurring osmolytes like trimethylamine-N-oxide (TMAO), to offset the deleterious effects of urea on the intracellular proteins in the urea-rich cells of elasmobranchs. However, using urea concentrations found in urea-rich cells of elasmobranches, we have found time-dependent effects on lactate dehydrogenase activity which indicate that TMAO plays the important biological role of slowing urea-induced dissociation of multimeric intracellular proteins. TMAO greatly diminishes the rate of lactate dehydrogenase dissociation and affords significant protection of the enzyme against urea-induced time-dependent inactivation. The effects of TMAO on enzyme inactivation by urea adds a temporal dimension that is an important part of the biology of the adaptation paradigm.

PMID:
9591689
PMCID:
PMC1299605
DOI:
10.1016/S0006-3495(98)77971-8
[Indexed for MEDLINE]
Free PMC Article

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