Characterisation of monolysocardiolipin acyltransferase activity

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Ma, Brian Jason Lap-Yen
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Cardiolipin (CL) is a unique phospholipid synthesised exclusively in the mitochondria where it is also mainly localised. Monolyso-CL acyltransferase is the enzyme responsible for re-acylating monolyso-CL to CL once a phospholipase A has removed one of the fatty acid tails. Because of CL's role in activating enzymes involved in energy metabolism, we investigated the effect of insulin on monolyso-CL acyltransferase activity and the composition of CL acyl groups. We hypothesised that some of the alterations in mitochondrial function may be due to the alteration in CL remodelling activity. Sprague-Dawley (SD) rats were treated with insulin (i.p. 12 U/rat) for 5 or 26 days. The hearts were then isolated and the mitochondrial fractions were collected. These mitochondria were assayed for monolyso-CL acyltransferase activity. In addition, streptozotocin-induced, diabetic SD rats were injected with saline for 5 days and the heart mitochondrial monolyso-CL acyltransferase activity was measured. The CL molecular species was examined. The characteristics of monolyso-CL acyltransferase activity from rat heart mitochondria were studied. In other experiments, the activity of monolyso-CL acyltransferase was localised using rat liver mitochondria. (Abstract shortened by UMI.)