Monoacylglycerol lipase activity in cardiac myocytes
Monoacylglycerol lipase activity in homogenates of isolated myocardial cells (myocytes) from rat hearts was recovered in both particulate and soluble subcellular fractions. The activity present in the microsomal (100 000 × g pellet) fraction was solubilized by treatment with Triton X-100 and combined with the 100 000 × g supernatant fraction; the properties of monoacylglycerol lipase were investigated with this soluble enzyme preparation. The Km for the hydrolysis of a 2-monoolein substrate was 16 μM. The rates of hydrolysis of 1-monoolein and 2-monoolein were identical, and 1-monoolein was a competitive inhibitor (Ki = 20 μM) of the hydrolysis of 2-monoolein. Monoacylglycerol lipase activity was regulated by product inhibition according to the following order of potency: fatty acyl CoA > free fatty acids > fatty acyl carnitine.