l-2,4-diaminobutyric acid decarboxylase activity responsible for the formation of 1,3-diaminopropane in Enterobacter aerogenes

High content of 1,3-diaminopropane (DAP), a normally minor derivative of polyamine metabolism, have been observed in cells of Enterobacter aerogenes. Supplementation of the growth medium with L-2,4-diaminobutyric acid (L-DABA) resulted in increased production of DAP, but not if supplemented with spermidine. On the basis of these observations, the biosynthetic route for DAP was evaluated. It has appeared that this bacterium possesses a novel enzyme activity catalysing the formation of DAP from L-DABA. Lack of the activity for oxidative cleavage of spermidine yielding DAP suggests that the enzyme termed DABA decarboxylase is responsible for the formation of DAP in this bacterium. The enzyme was partially purified 360-fold and some properties were examined. The pH optimum for the activity was 7.75-8.0, and the enzyme showed an absolute requirement for pyridoxal 5'-phosphate with the Km value of 41 microM. The Km value for L-DABA was 0.32 mM, and neither L-2,3-diaminopropionic acid, L-ornithine nor L-lysine showed detectable substrate activity towards the partially purified enzyme. Mg2+ and dithiothreitol greatly activated the enzyme.     

Discovery of dicephalosterol, a new testosterone 5α-reductase inhibitor, and some new mycological aspects of its producer,Dicephalospora rufocornea (sclerotiniaceae, discomycetes)

Dicephalosterol, a new testosterone 5α-reductase inhibitor, was found from isolates ofDicephalospora rufocornea, a sclerotiniaceous discomycete widely distributed, but not previously cultured. Under SEM observation, the polar appendage of the ascospores inD. rufocornea was found to be more solid than was hitherto reported. Dicephalosterol was produced by submerged fermentation for 7 d. This new analogue of testosterone showed an IC₅₀ of 5.7 μg/ml for rat prostatic 5α-reductase, but no antimicrobial activity against bacteria or fungi.