AJP - Cell Physiology, Vol 246, Issue 3 266-C270, Copyright © 1984 by American Physiological Society
Cytosolic lysophospholipase in cardiac myocytes and its inhibition by L-palmitoyl carnitine
R. W. Gross, G. G. Ahumada and B. E. Sobel
Since lysophosphatides have been implicated as arrhythmogenic metabolites,
modulation of their catabolism in cardiac myocytes has been characterized.
Rat cardiac myocytes and mesenchymal cells grown in culture were found to
contain cytosolic lysophospholipase with specific activities of 1.3 +/- 0.1
and 0.9 +/- 0.1 nmol X mg-1 X min-1, respectively. Rat myocytic
lysophospholipase had a molecular mass of approximately 20,000 daltons,
estimated by gel filtration chromatography. Kinetic analysis of cytosolic
myocytic lysophospholipase demonstrated a Michaelis constant of 11 microM,
a pH optimum of 8.0, and competitive inhibition by L-palmitoyl carnitine
(inhibitory constant of 12 microM). Although lysophospholipase-transacylase
activity could not be detected in rat myocyte or mesenchymal cell cultures,
rabbit myocytes isolated by perfusion of isolated hearts with collagenase
contained lysophospholipase-transacylase in cytosolic extracts with a
specific activity of 0.2 nmol X mg-1 X min-1. These results demonstrate the
presence of lysophospholipase in cardiac myocytes and suggest that the
increase in long-chain acyl carnitine, which occurs during myocardial
ischemia, may contribute to accumulation of lysophosphatides within cardiac
myocytes.
