An extracellular cholesterol oxidase (cho) enzyme was isolated from the Streptomyces parvus, a new source and purified 18-fold by ion exchange and gel filtration chromatography. Specific activity of the purified enzyme was found to be 20 U/mg with a 55 kDa molecular mass. The enzyme was stable at pH 7.2 and 50 °C. The enzyme activity was inhibited in the presence of Pb(2+), Ag(2+), Hg(2+), and Zn(2+) and enhanced in the presence of Mn(2+). The enzyme activity was inhibited by the thiol-reducing reagents (DTT, β-mercaptoethanol), suggesting that disulfide linkage is essential for the enzyme activity. The enzyme activity was found to be maximum in the presence of Triton X-100 and X-114 detergents whereas sodium dodecyl sulfate fully inactivated the enzyme. The enzyme showed moderate stability towards all organic solvents except acetone, benzene, chloroform and the activity increased in the presence of isopropanol and ethanol. The K(m) value for the oxidation of cholesterol by this enzyme was 0.02 mM.

No abstract

Aims:  To isolate and characterize bioactive metabolites produced by a micro‐organism isolated from a soil sample associated with the roots of a medicinal plant, Azadirachta indica. Methods and Results:  Morphological, cultural, physiological and 16S rRNA homology studies revealed that the organism showed 99% similarity with Streptomyces griseoruber NBRC 12873. One bioactive metabolite (Py2) isolated from the fermented broth was characterized as actinomycin‐D (act‐D). It showed high activity against various Gram‐positive and Gram‐negative bacterial cultures, Mycobacterium tuberculosis H37Rv and human neoplastic cells in vitro using standard protocols. Conclusions:  The isolated strain S. griseoruber produced act‐D predominantly (210 mg l−1, c. 88% of the crude) under nonoptimized growth conditions. Significance and Impact of the Study:  Streptomyces griseoruber may be exploited as a potential source for the commercial production of act‐D, as this strain is not reported to produce act‐D. Further investigations on the strain for commercial application will be of immense pharmaceutical importance.

During the search for a potent antifungal drug, a cell-permeable metabolite was isolated from a soil isolate taxonomically identified as Penicillium radicum. The strain was found to be a potent antifungal agent. Production conditions of the active compound were optimized and the active compound was isolated, purified, characterized and identified as a phosphoinositide 3-kinase (PI3K) inhibitor, commonly known as wortmannin (Wtmn). This is very first time we are reporting the production of Wtmn from P. radicum. In addition to its previously discovered anticancer properties, the broad spectrum antifungal property of Wtmn was re-confirmed using various fungal strains. Virtual screening was performed through molecular docking studies against potential antifungal targets, and it was found that Wtmn was predicted to impede the actions of these targets more efficiently than known antifungal compounds such as voriconazole and nikkomycin i.e. 1) mevalonate-5-diphosphate decarboxylase (1FI4), responsible for sterol/isoprenoid biosynthesis; 2) exocyst complex component SEC3 (3A58) where Rho- and phosphoinositide-dependent localization is present and 3) Kre2p/Mnt1p a Golgi alpha1,2-mannosyltransferase (1S4N) involved in the biosynthesis of yeast cell wall glycoproteins). We conclude that Wtmn produced from P. radicum is a promising lead compound which could be potentially used as an efficient antifungal drug in the near future after appropriate structural modifications to reduce toxicity and improve stability.

An actinomycin-D producing strain was isolated from soil and characterized as Streptomyces sindenensis. The culture was subjected to UV irradiation and a mutant with 400% higher actinomycin-D production was isolated (400 mg/l -1 as compared to 80 mg/l -1 produced by the parent). Production medium was optimized and antibiotic yield with the mutant was enhanced to 850 mg/l -1 which is 963% higher as compared with the parent.