Two isoforms of glutamate decarboxylase (GAD(65kDa) and GAD(67kDa)) from human brain, which had previously been overexpressed in Escherichia coli as fusion proteins containing a glutathione-S-transferase domain, were purified by affinity chromatography on glutathione Sepharose 4B. Both isoforms were also expressed in Saccharomyces cerevisiae. After modification of a HPLC based assay, the enzymes were characterized with respect to their biochemical properties. Comparison of kinetic data, pH, and temperature optima as well as of the mode of interaction with pyridoxal phosphate as a cofactor revealed several significant differences between the two isoenzymes reflecting their somewhat different physiological and molecular features. Investigation of the influence of 4'-O-methylpyridoxine (ginkgotoxin) (1), a neurotoxin occurring in Ginkgo biloba L., on the different isoenzymes, indicates that the phosphorylated form of the toxin, 4'-O-methylpyridoxine-5'-phosphate (2), decreases GAD(65kDa) activity, although in unphysiologically high concentrations, whereas GAD(67kDa) activity seems to be hardly affected.

Wood from three different plants of the Celastraceae growing in their natural habitats in Brazil (Maytenus aquifolia Mart.) and South Africa [Putterlickia retrospinosa van Wyk and Mostert, P. verrucosa (E. Meyer ex Sonder) Szyszyl.] was established as a source of endophytic bacteria using a medium selective for actinomycetes. Two isolates were identified as Streptomyces setonii and S. sampsonii whereas two others were not assignable to any of the known Streptomyces species. They were preliminarily named Streptomyces Q21 and Streptomyces MaB-QuH-8. The latter strain produces a new chloropyrrol and chlorinated anthracyclinone. The chloropyrrol showed high activity against a series of multiresistent bacteria and mycobacteria.

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