Proline biosynthesis

Progeslerone, structure and function of, 1083 Progestin, 1082 function of. 1082 Proline, biosynthesis of, 932... 

Smith, C.J. Deutch, A.H. Rushlow, K.E. Purification and characteristics of a y-glutamyl kinase involved in Escherichia coli proline biosynthesis. J. Bacteriol., 157, 545-551 (1984)... 

Hayzer, D.J. Moses, V. The enzymes of proline biosynthesis in Escherichia coli. Their molecular weights and the problem of enzyme aggregation. Biochem. J., 173, 219-228 (1978)... 

Yaklichkin, S.Y. Zimina, M.S. Neumyvakin, L.V, Proline biosynthesis gene proB of thermophilic bacterium Thermus ruber cloning, sequencing, and properties of encoded y-glutamylphosphate kinase. Mol. Biol., 33, 628-635 (1999)... 

Chart 8 Proline biosynthesis in trematodes (abbreviations a, arginase b, omithine-a-... 

Enzymes catalyze almost every metabolic reaction in extant cells. A few tmusually facile reactions, such as cyclization of L-glutamate 7-semialdehyde to form pyrroline-5-carboxylate in the proline biosynthesis pathway and decarboxylation of 2-amino-3-oxo-4-phosphonooxybutyrate in the pyridoxal phosphate (PLP) synthesis pathway, do not require acceleration to satisfy the demands of the cell. For all other reactions, catalysis is required because the rates of nonenzymatic reactions are very slow. Modern enzymes are marvelous catalysts. They accelerate reactions by up to 20 orders of magnitude, prevent side reactions of reactive intermediates, and catalyze stereoselective and stereospecific reactions. Further, they are often exquisitely regulated by small molecule ligands. 

Proline accumulation in salt-stressed cells may result from an increased rate of synthesis and a decreased rate of utilization, a relaxation of feedback inhibition over proline biosynthesis was suggested to contribute to this increased rate of synthesis (Liu and Hellebust, 1976c). 

Aral B, Schlenzig JS, Liu G, Kamoun P. Database cloning human delta 1-pyrroline-5-carboxylate synthetase (P5CS) cDNA a bifunctional enzyme catalyzing the first 2 steps in proline biosynthesis. Comptes Rendus de V Academic des Sciences, Serie III, Sciences de La Vie 1996 319(3) 171-178... 

The metabolic pathways with P5C as the central intermediate (Fig. 2) were initially defined as a system for proline biosynthesis (1, 2, 5) and this physiologic endpoint has been emphasized by a number of investigators (65, 92, 123). In both prokaryotes (5) and eukaryotes (6, 93, 99) the inability to synthesize P5C results in proline auxotrophy. On the other hand if one of the pathways for P5C synthesis is present, i.e., from either ornithine or glutamate, normal growth occurs in proline-free medium (93J. Because of its strategic location in intermediary metabolism investigators have hypothesized that this metabolic system mediates... 

With the exception of the last enzyme in the pathway, pyrroline-5-carboxyl-ate reductase (13) (e.g., Krueger et al, 1986), little is known about the enzymes associated with proline biosynthesis in higher plants. All of the detectable activity of the reductase was found in pea chloroplasts (Rayapati and Stewart,... 

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