Presqualene metabolism in two species of Lagenidium.

The fate of precursors of the isoprenoid pathway was studied in the sterol auxotroph Lagenidium giganteum and in the positive control organism Lagenidium callinectes. Acetate derived from glucose and mevalonic acid was converted to sterols and fatty acids in L. callinectes. Lagenidium giganteum converted mevalonic acid to sterols and fatty acids, but glucose-derived acetate was not utilized for sterol synthesis. The results showed that the defect in the isoprenoid pathway of L. giganteum occurs at the level of the beta-hydroxy-beta-methylglutarylcoenzyme A reductase-synthase complex. Various aspects of this defect are discussed relative to metabolism of the organism.

Biochemical activities of entomophagous fungi.

This review is directed toward the study of the physiology and biochemistry of parasitic fungi on insects and stresses the usefulness and utility of these organisms from the standpoint of applied research and biotechnology. The review covers the principal contributions made by investigators toward elucidation of the infective mechanisms of the entomogenous fungi, and the various biochemical attributes of these organisms. The interplay of the various enzymes and associated biochemical substances which are involved in the infective process is discussed as well as the important studies of the peculiar physiology frequently associated with these microorganisms.

The extracellular acid phosphatase of the mosquito-parasitizing fungus Lagenidium giganteum.

The mosquito-parasitizing fungus Lagenidium giganteum secreted a soluble acid phosphatase and beta-D-glucosidase into the growth medium. The acid phosphatase was isolated and purified to single component, and some of its physicochemical properties were determined. The enzyme exhibited a pH optimum of 5.6 in phthalate buffer with p-nitrophenyl phosphate and was temperature-inactivated at 55 degrees C. Enzyme activity seems to be limited to phenyl-phosphate substrates. A molecular weight of 42,800 was found and the amino acid content was also determined. A Km for p-nitrophenyl phosphate of 1.6 x 10(-7) M was found. The possible involvement of the enzyme in the infective process was discussed.

Reversed-phase thin layer chromatography of some common sterols.

The chromatographic mobilities of 17 sterols and squalene on reversed-phase thin layer plates with four nonaqueous solvent systems is described. A degree of separation adequate to identify several of the sterols was obtained. It was possible to separate the pairs: cholestanol, epicholestanol; coprostanol, epicoprostanol; 5 beta-cholestan-3 alpha and 3 beta-ol and lanosterol, dihydrolanosterol.

Fungal transformations of triparanol.

Fungal transformations of triparanol, a hypercholesterolemic drug, were studied in Lagenidium giganteum and Lagenidium callinectes. The products were identified by combined gas chromatography-mass spectrometry. Two metabolites were observed from each organism; only one of the metabolites was found in both organisms.

Cycloartenol-derived sterol biosynthesis in the Peronosporales.

Selected species of the order Peronosporales, which are unable to epoxidize squalene and thus synthesize sterols, are able to metabolize exogenous cycloartenol to lanosterol and in some organisms to fucosterol, ergosterol, and cholesterol. Lanosterol was less effectively utilized but some ergosterol and cholesterol were yielded. Fucosterol was very efficiently metabolized by most species to ergosterol, Delta(7)-ergostenol, Delta(5)-ergostenol, cholestanol, and cholesterol. Several unknown sterols were observed in most trials. These data suggest a vestigial sterol synthetic pathway derived from cycloartenol, followed by possible isomerization to lanosterol and then to other sterols.