Monoacylglycerol hydrolase activity of isolated rat small intestinal epithelial cells.

1. Albumin is the preferred stabilizer of the higher monoacylglycerol substrates, since the highest activity was measured with albumin rather than with Triton X-100 or other detergents tested. 2. The monoacylglycerol hydrolase activity may be strongly influenced by the amount of albumin used as the only emulsifier. Possible models for the physical states of the substrate are discussed. 3. The reaction rates with 1- and 2-monoacylglycerols are generally similar but may vary according to the physical states of the substrates. 4. The same enzyme hydrolyzes both 1- and 2-isomers since the hydrolytic activities were found to be competitive rather than additive. For both isomers identical apparent Km values less than 0.1 mM were obtained. 5. A comparison of the rates of hydrolysis of 1- and 2-monopalmitoylglycerol by the villus preparation at various temperatures confirmed that generally the reaction rates are similar and that the energy of activation is about 15 kcal/mol, so that the Q10 is about 1.8. 6. It is speculated that the microsomal level of long-chain acyl-CoA is an important determinant in the fate of the resorbed monoacylglycerol, since acylCoA is not only a substrate for the reacylation reactions but also an inhibitor of monoacylglycerol hydrolase.