This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Tang, S. L. Articles by Howard, D. H. Search for Related Content PubMed PubMed Citation Articles by Tang, S. L. Articles by Howard, D. H.

Uptake and Utilization of Glutamic Acid by Cryptococcus albidus

Department of Microbiology and Immunology, School of Medicine, University of California, Los Angeles, California 90024

ABSTRACT

Cryptococcus albidus utilizes glutamate as a sole carbon source. The kinetics of uptake of this amino acid were studied. L-Glutamic acid was taken up by two saturable systems: a high affinity system with a Michaelis constant (K_m) of 1.15 x 10^–5 M and a V_max of 0.049 µmol per mg per h and a low affinity system with a K_m of 2.5 x 10^–3 M and a V_max of 3.61 µmol per mg per h. Both systems possessed characteristics of active transport which were dependent on temperature and pH and which required metabolic energy. Uptake was inhibited at 37 C but the temperature-sensitive step was reversible. Chemical fractionation of cells with 5% trichloroacetic acid showed that glutamic acid initially entered a soluble pool which decreased after 1 h as the amino acid was incorporated into the protein and nucleic acid fractions of the yeast. Some of the glutamate was completely oxidized and could be recovered as ¹⁴CO₂. Therefore, the amino acid was also used as an energy source.