[Formation of hemichrome during reaction of hemoglobin with polar phosphatidylcholine derivatives].

Polar phosphatidylcholine derivatives [1-acyl-2-lyso-sn-glycero-3-phosphocholine, 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine (platelet-activating factor), 1-acyl-2-glutaryl-sn-glycero-3-phosphocholine, and 1-acyl-2-azelaoyl-sn-glycero-3-phosphocholine], which are formed in biological structures by enzymatic and free-radical reactions, were studied as effectors of the conversion of methemoglobin and oxyhemoglobin into an oxidized low-spin form referred to as hemichrome. It is shown that all these phosphatidylcholine derivatives act as effectors in the course of the transition of met- and oxyhemoglobin to hemichrome. Among the compounds studied, phosphatidylcholine derivatives containing glutaric and azelaic acids residues have the greatest effect on the rate of hemichrome formation.

[Effects of fatty acid amides on phosphatidylcholine hydrolysis catalyzed by phospholipase A2 in micelles].

The effect of fatty acid amides on the hydrolysis of natural phosphatidylcholine and its semisynthetic analog, dioleoyl phosphatidylcholine, catalyzed by phospholipase A2 in mixed micelles with Triton X-100 has been studied. Palmitoylamide, oleoylamide, and stearoylamide were shown to be the inhibitors of enzymatic phospholipid hydrolysis.

[The use of hemoglobin for determination of phospholipase A2 activity].

A spectrophotometric method is proposed for determining phospholipase A2 activity, which is based on the conversion of hemoglobin into hemichrome under the fatty acid action. The spectral difference between hemoglobin and hemichrome was registered by the difference spectrum with a minimum at 405 nm and a maximum at 423 nm. The absorption value determined as the difference between the spectrum maximum and minimum was proportional to the amount of the fatty acid derived from hydrolysis of phospholipids.

[Initiation of lipid peroxidation as a result of hemoglobin transformation into hemichrome induced by free fatty acids].

The effects of free fatty acids on hemoglobin conversion and lipid peroxidation were studied in hemoglobin-containing liposomes (hemosomes) formed from an equimolar mixture of phosphatidylcholine (PC) and phosphatidylethanolamine (PE). It was shown that in hemosomes oxyhemoglobin is converted into hemichrome by the interaction of saturated fatty acids (arachidic, stearic, palmitic, myristic and lauric). This is accompanied by accumulation of primary and secondary products of lipid peroxidation.