Purification and characterization of lysophospholipase-transacylase of pathogenic fungus Candida albicans

A lysophospholipase-transacylase was purified to homogeneity from the culture broth of Candida albicans by ammonium sulfate precipitation and chromatographs on DEAE-cellulose, Ultrogel AcA-44, first Mono Q, hydroxyapatite, TSKgel-3000 and second Mono Q columns. The purified protein was a single band (Mr 41,000) as inferred by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It had a specific activity of 78 mumol/min per mg protein for fatty acid release and 320 mumol/min per mg protein for phosphatidylcholine formation. Fatty acid release obeyed Michaelis-Menten kinetics and the apparent Km was 76 microM of 1-palmitoyl-sn-glycero-3-phosphatidylcholine, but Lineweaver-Burk plots of transacylase activity was parabolic. The ratio of hydrolase to transacylase activity of the purified enzyme was varied depending upon the concentration of lysophosphatidylcholine. Transacylation was prominent at high concentration of substrate and the ratio of hydrolase to transacylase was 0.24. Low concentration of palmitoylcarnitine (50 microM) inhibited markedly phosphatidylcholine formation but stimulated fatty acid release. The degree of esterification of 1-acyllysophosphatidylcholine was altered with mixtures of different molecular species of substrate, demonstrating acyl chain selectivity in the transfer process. These results suggest that C. albicans lysophospholipase-transacylase is different from the corresponding mammalian enzymes in enzymatic properties.     

New carotenoids from the thermophilic green sulfur bacterium Chlorobium tepidum: 1′,2′-dihydro-γ-carotene, 1′,2′-dihydrochlorobactene, and OH-chlorobactene glucoside ester, and the carotenoid composition of different strains

The complete carotenoid composition of the thermophilic green sulfur bacterium Chlorobium tepidum strain TNO was determined by spectroscopic methods. Major carotenoids were four kinds of carotenes: γ-carotene, chlorobactene, and their 1′,2′-dihydro derivatives (1′,2′-dihydro-γ-carotene and 1′,2′-dihydrochlorobactene). In lesser amounts, hydroxyl γ-carotene, hydroxyl chlorobactene, and their glucoside fatty acid esters were found. The only esterified fatty acid present was laurate, and OH-chlorobactene glucoside laurate is a novel carotenoid. In other strains of C. tepidum, the same carotenoids were found, but the composition varied from strain to strain. The overall pigment composition in cells of strain TNO was 4 mol carotenoids and 40 mol bacteriochlorophyll c per mol bacteriochlorophyll a. The effects of nicotine on carotenoid biosynthesis in C. tepidum differed from those in the thermophilic green nonsulfur bacterium Chloroflexus aurantiacus. Received: 3 February 1997 / Accepted: 6 June 1997