Showing papers by "Rama Shanker Verma published in 1983"

Transport of purine, pyrimidine bases and nucleosides in Candida albicans, a pathogenic yeast.

Abstract: Saturable, carrier mediated transport mechanism of adenine, guanine, thymine, uracil, adenosine, inosine, thymidine and uridine has been characterized in Candida albicans cells. Analysis of intracellular contents at short and long time intervals and kinetic data revealed that the uptake of all these bases and their nucleosides is independent of phosphoribosyltransferases and phosphorylases and their metabolic conversion starts only after an initial lag of 1-2 minutes. On the basis of competition experiments, different common and specific transport systems have also been identified.

Absence of derepression of amino acids transport in Candida.

Abstract: The transport of glycine, L-alanine, L-proline, L-leucine, L-lysine, L-phenylalanine and L-glutamic acid did not enhance in various strains of Candida cells, when they were grown in proline containing medium or preincubated with proline. However, under similar conditions, a significant enhancement in the level of accumulation of amino acids (derepression) was observed in Saccharomyces cerevisiae X-2180-A2 (GAP+) cells, which was sensitive to ammonium ions (NH4+). As expected, the derepression was absent in GAP- cells of S. cerevisiae X-2180 (GAP- mutant). In contrast to S. cerevisiae (GAP+) cells, the increase in few amino acids uptake in different Candida strains, grown in proline or preincubated in proline, could not be inhibited by cycloheximide, NH4+ or their D-stereoisomers. It appears that derepression of amino acids transport, a well known phenomenon in S. cerevisiae, may not exist in Candida species.