Kinetic Properties of Plasmalogenase From Bovine Brain¹

Plasmalogenase was assayed by measuring the disappearance of the plasmalogen by two‐dimensional thin‐layer chromatography. The enzyme was present in a glycerol‐bicarbonate extract of an acetone‐dried powder from bovine brain. With ethanolamine plasmalogens as the substrate, the K m was 180 μM. Diacyl glycerophosphorylcholines, diacyl glycerophosphorylethanolamines and choline plasmalogens were competitive inhibitors. With choline plasmalogens as the substrate, the K m was 208 μM and competitive inhibition was observed with diacyl glycerophosphorylcholines and ethanolamine plasmalogens. The same enzyme may be responsible for the hydrolysis of the alk‐1‐enyl moiety from both plasmalogens. Plasmalogenase activity was 5.1 μmol/h/g of dog brain, 3.9 μmol/h/g of rat brain and 3.4 μmol/h/g of gerbil brain. A lysophospholipase was also found in the glycerol‐bicarbonate extract from the acetone‐dried powder. The lysophospholipase was more active in hydrolysing acyl groups from 2‐acyl‐ sn ‐glycero‐3‐phosphorylethanolamines than the plasmalogenase was active in hydrolyzing alk‐1‐enyl groups from 1‐alk‐1′‐enyl‐2‐acyl‐ sn ‐glycero‐3‐phosphorylethanolamines.