Biosynthesis with cell organelle

One of the first stages of the chemicals effect on a cell consists in its link with a receptor. Then, the signal about this event may be transferred to other intracellular components in cytoplasm or nucleus. This, in its turn, causes changes in cell activity, namely its biosynthetic activity and the activities of individual enzymes, their complexes, and even whole organelles. In an intricate process of cell response to a signal, a key role belongs to bioprotein and the biosynthesis of its derivatives. Therefore, analysis of ES and IPG effect on mitotic activity and cell sizes of the regenerating liver as well as protein synthesis dynamics is of particular importance. 

Whereas DNA is mostly located in the nucleus of cells in higher organisms (with some also in mitochondria and in plant chloroplasts), RNA has a much broader cellular distribution. RNA comes in three major and distinct forms, each of which plays a cmcial role in protein biosynthesis in the ribosome, the intracellular organelle which is the site of protein biosynthesis. Ribosomal RNA (rRNA) represents two-thirds of the mass of the ribosome, messenger RNA (mRNA) encodes the information for the amino acid sequence of proteins, while transfer RNAs (tRNAs) serve as adaptor molecules, allowing the four-letter code of nucleic acids to be translated into the 20-letter code of proteins. The tRNA molecules contain a substantial number of modified bases, which are introduced by specific enzymes. 

PG is made in mitochondria and microsomes of animal cells and appears to be primarily converted to DPG. DPG is biosynthesized exclusively on the matrix side of the mitochondrial inner membrane and is found only in this organelle. There is evidence that the rate-limiting step in DPG biosynthesis is the conversion of PA into CDP-DG (G.M. Hatch, 1994). Consistent with this idea, the levels of CTP regulate DPG biosynthesis in cardiac myoblasts (G.M. Hatch, 1996). Using techniques developed by Raetz and co-workers [14], a temperature-sensitive mutant of PG-P synthase in CHO cells was isolated (M. Nishijima 1993). The mutant had only 1% of wild-type PG-P synthase activity at 40°C and exhibited a temperature-sensitive defect in PG and DPG biosynthesis. This mutant was used to show that DPG is required for the NADH-ubiquinone reductase (complex I) activity of the respiratory chain. 

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