Action of phospholipase B on ultrasonically dispersed lecithin

Lipid metabolism in fungi

So far, reviews that have appeared on fungal lipids present data mainly on the lipid composition of these organisms and the influence of lipids on their physiology. These reviews provide little information about the enzymes of lipid metabolism in these organisms and it is assumed, by most workers, that lipid synthesis in all fungi takes place as in Saccharomyces cervesiae, the only fungus in which the complete pathways of phospholipid biosynthesis have been worked out. During the last few years, literature has accumulated on lipid metabolic enzymes of other fungi, as investigators became increasingly interested in this area of research. The present review, after an introduction, will be divided into different sections and each section will deal, comparatively, with various aspects of fungal lipid metabolism and physiology. This review will, therefore, bring out the differences or similarities of lipid metabolism in diverse fungal species.

Phospholipase activity of sea urchin sperm: its possible involvement in membrane fusion

Phospholipase activity of egg-water treated Arbacia punctulata and Lytechinus variegatus sperm was shown to result from the sequential action of phospholipase A and lysophospholipase. A transient burst of phospholipase A activity followed induction of the acrosome reaction with egg water. The time of appearance suggested an acrosomal localization of the enzyme. The peak activity of phospholipase A correlated with initiation of sperm-egg fusion, suggesting a role for sea urchin sperm phospholipase A in membrane fusion and/or egg activation during fertilization.

Relation of in vitro inhibition by chelates of Clostridium perfringens alpha-toxin to their ability to protect against experimental toxemia

The inhibition of Clostridium perfringens alpha-toxin by ethylenediaminetetraacetate (EDTA) and diethylenetriaminepentacetate (DTPA) was studied utilizing three different in vitro assay procedures: diffusion on egg yolk-agar, disintegration of muscle sections, and manometric assay with partially purified lecithin as substrate. DTPA was 10 to 20 times more efficient as an inhibitor than EDTA in systems containing relatively large amounts of calcium; these observations were similar to those observed in previous in vivo protection studies. A number of other chelating agents were tested for their ability to inhibit alpha-toxin in vitro and protect mice against it; the chelating agents which were the most efficient in vitro inhibitors had the greatest in vivo protective ability.

PROPERTIES OF THE PHOSPHOLIPASE B FROM PENICILLIUM NOTATUM

Phospholipase B from Penicillium notatum catalyzed rapid deacylation of purified egg lecithin, in the absence of any activators, when the substrate was ultrasonically dispersed. The rate of enzymic hydrolysis depended on the degree of dispersion of the substrate and also on its degree of unsaturation. Decrease in acyl ester groups was accompanied by release of water-soluble phosphate identified as glycerylphosphorylcholine; no lysolecithin was detected by thin-layer chromatography at any stage of the reaction. The optimum pH in acetate buffer was 4.0, and the apparent Kmwas 6.3 mM for the ultrasonically dispersed substrate. The enzyme attacked lysolecithin more rapidly than lecithin. Enzymic activity was not affected by iodoacetate, cyanide, or cystine, but was strongly inhibited by glutathione, cysteine, thioglycollate, ferrous and ferric ions, or by prolonged dialysis. Inhibition by glutathione was completely reversed by ferricyanide. These results suggest that the enzyme requires —S—S— linkages for activity.