Regulation of biosynthesis of secondary metabolites

Partially purified citrate synthase (EC 4.1.3.7) was isolated from submerged mycelium ofStreptomyces aureofaciens RIA 57, a strain producing chlortetracycline. Enzymatic activity was determined spectrophotometrically by means of 5,5′-dithio-bis-(2-nitrobenzoic acid). Citrate synthase was inhibited by ATP, inhibition being competitive with respect to acetyl coenzyme A. In 5mm concentration, ATP caused 55% inhibition of the enzyme. ADP, in the same concentration, caused 30% inhibition, while AMP caused none. Other natural nucleoside di- and triphosphates, in 1–5mm concentration, did not significantly affect citrate synthase inStreptomyces aureofaciens. Mg²⁺ inhibited the activity of the enzyme, but also reduced the negative effect of ATP. The role of ATP in regulation of the metabolic paths of acetyl CoA is discussed.     

Elemental Composition of Gonads,Gametes and Larvae in Black and Brown Morphs of the Bivalve Mollusk Mytilus galloprovincialis LAM

Journal of Evolutionary Biochemistry and Physiology - Contents of the bulk and trace elements were determined in male and female gonads, gametes (sperm and oocytes), and larvae (trochophores) of...     

Domoic acid production by Pseudo-nitzschia calliantha Lundholm, Moestrup et Hasle (bacillariophyta) isolated from the Black Sea

A species of Pseudo-nitzschia isolated from Sevastopol Bay, Black Sea, was examined for its toxicity. The species was identified as P. calliantha Lundholm, Moestrup et Hasle based on SEM and TEM examination. Domoic acid (DA) was detected in batch culture throughout the growth cycle of P. calliantha. The production of DA by this diatom species was confirmed by fluorenylmethoxycarbonyl (FMOC) derivatization and HPLC-fluorescence method. The cellular DA level was higher in the early exponential phase, with the maximum value of 0.95 pg DA cell⁻¹. In the stationary phase, the cellular DA levels declined. This is the first record of a DA producing diatom isolated from the Black Sea.     

Benthic Diatoms of the Russian Waters of the Sea of Japan and Adjacent Sea Areas

Russian Journal of Marine Biology - This review analyzes the current state of knowledge of the microphytobenthos in the Russian waters of the Sea of Japan and adjacent sea areas. A retrospective...