Comparative study of enzymes related to proline metabolism in tepary bean (Phaseolus acutifolius) and common bean (Phaseolus vulgaris) under drought and irrigated conditions, and various urea concentrations.

There are several mechanisms used by plants for survival in adverse environments such as drought, high temperature and salinity. The objective of this study was to evaluate the drought tolerance of tepary bean as a function of biochemical processes linked to isozyme synthesis and changes in enzymatic activity related to proline metabolism. Mature seeds of common beans var. flor de mayo, Phoseolus vulgaris and tepary beans Phaseolus acutifolius were grown under two water conditions (irrigation and drought), and four levels of urea. Vertical electrophoresis and spectrophotometric techniques were used to evaluate protein patterns, glutamate dehydrogenase (GDH), proline oxidase (PO) and pyrroline-5-carboxylate reductase (P5C reductase) enzyme activities. These enzymes were studied because they are directly related to protein synthesis. Electrophoretic patterns showed more proteins in tepary beans than in common beans with limited irrigation. GDH showed only one isozyme, with a molecular weight between 240) to 270 kDa. A decrease in PO activity was observed in common beans under drought stress with a value of 237 micromol/min, in comparison to irrigation conditions of 580 micromol/min. GDH and P5C reductase enzymes have had higher activity in common beans than in tepary beans under water stress. There was a significant difference only in glutamate dehydrogenase enzyme with respect to urea level. The results suggest that drought tolerance of tepary beans is due to biochemical processes related to proline metabolic enzymes.

Schistosoma mansoni: higher free proline levels in the livers of infected mice.

The concentration of L-hydroxyproline in the liver of ICR female mice increased rapidly during the 8th to 11th weeks of Schistosoma mansoni infection. Free L-proline concentration began to increase about the 7th week and reached its maximum at the 8th to 9th weeks of the infection, when the granulomatous response to the schistosome eggs in the liver was most prominent, as indicated by the increase in liver wet weight and its deoxyribonucleic acid concentration. A significant increment in the total activity of ornithine-delta-transaminase (EC 2.6.1.13) and the decrease in the specific activity of proline oxidase (EC 1.4.3.2) became detectable in the liver homogenate of infected mice on the 8th week. However, changes in these enzymatic activities were not parallel to that of the hepatic free L-proline content. Intraperitoneal administration of S. mansoni egg granulomas or 15,000g x 30 min supernatant fluid of their extracts into uninfected, normal mice significantly increased the hepatic free L-proline content without any appreciable effect on the enzymatic activities of proline oxidase and ornithine-delta-transaminase. These findings suggest that S. mansoni egg granulomas contain a factor(s) which may be responsible for the elevation of free L-proline content in the fibrotic liver caused by experimental schistosomiasis mansoni.

Effect of dietary proline on proline metabolism in the neonatal pig.

The effect of two dietary concentrations of proline (10.3 and 15.8 g/kg) on proline-metabolizing enzymes [pyrroline-5-carboxylate (P5C) reductase and proline oxidase], plasma and tissue free proline concentrations and growth were investigated in the 2- to 13-d-old pig. Diet had no effect on growth or enzyme activity. Diet had a significant (P less than 0.05) effect on the concentration of free proline in plasma, liver, intestine and muscle, but no effect in kidney. These data suggest that the magnitude and pattern of change of P5C reductase activity is not influenced by the concentration of proline in the diet. The lower plasma and tissue free proline concentrations in the piglets fed the basal diet compared with piglets fed the proline-supplemented diet and the lack of effect of diet on enzyme activity suggest there was inadequate proline in the basal diet, and those piglets were unable to increase proline synthesis to maintain normal proline concentrations.