The substrate specificity of phospholipase A

Abstract

Investigations on variously modified analogues of phospholipids elucidated the following substrate characteristics for phospholipase A (Crotalus adamanteus).

1. 1. Within the class of α-phosphoglycerides -isomers are readily hydrolysed, while -α-phospholipids appeared not to be attacked.

2. 2. -α-Lecithins containing fatty acids with greatly varying chain length are susceptible to phospholipase A action; however, certain water-soluble short-chain compounds are hydrolysed at a very slow rate only.

3. 3. Aside from effects on the surface charge of the phosphoglyceride micelles the nature of the polar headgroup esterified to the phosphoryl moiety turned out not to form any prerequisite, and its presence even appeared to be dispensible.

4. 4. Contrary to a blocking of the amino function, protection of the hydroxyl function of phosphatidylethanolamine caused an inactivation of the substrate properties.

5. 5. Both, a γ-benzyl-β-acyl-α-phosphoglyceride and a β-acyl-lyso derivative, were hydrolysed, whereas the corresponding structural isomers carrying the fatty acid in γ-position appeared not to be susceptible to phospholipase A action.

6. 6. Glycol analogues were demonstrated to exhibit substrate activity.

7. 7. Phospholipase A catalyses the hydrolysis of a symmetric β-lecithin into an optical-active lysolecithin.

8. 8. An isolated specimen of cardiolipin was hydrolysed, whereas sphingomyelin resisted phospholipase A action.