Uptake of L-proline by Histoplasma capsulatum.
The uptake and incorporation of L-proline by yeast cells of the dimorphic zoopathogen Histoplasma capsulatum were studied. The amino acid was assimilated in at least two ways: by an active transport system with a Km of 1.7 X 10(-5) M and by simple diffusion. The active transport system was sterospecific and severely restricted to neutral aliphatic side-chain amino acids. Certain analogues inhibited L-proline uptake and prevented incorporation of the amino acid into cellular constituents. The inhibition of L-proline uptake by L-leucine was competitive. Since L-leucine and L-proline are seemingly transported by a system with similar characteristics, must be concluded, as originally postulated, that the buckled ring of L-proline, in solution, acts as an aliphatic side chain and that this cyclic amino acid is transported by a system more or less specific for amino acids with neutral aliphatic side chains.
D000596:Amino Acids / Q000378:metabolism; D001383:Azetidinecarboxylic Acid / Q000378:metabolism; D001693:Biological Transport, Active; D002264:Carboxylic Acids / Q000378:metabolism; D004058:Diffusion; D006658:Histoplasma / Q000378:metabolism*; D007930:Leucine / Q000378:metabolism; D011392:Proline / Q000031:analogs & derivatives / Q000378:metabolism*; D012521:Sarcosine / Q000378:metabolism; D013237:Stereoisomerism
D000596:Amino Acids; D002264:Carboxylic Acids; D001383:Azetidinecarboxylic Acid; D011392:Proline; D007930:Leucine; D012521:Sarcosine