ENERGY-METABOLISM IN LEISHMANIA

Alanine plays a key role in the response of promastigotes to osmotic s tress and to hypoxia. It is rapidly released in response to hypo-osmol ality, is consumed from its large intracellular pool under iso-osmotic conditions even in the presence of glucose, and is synthesized under hyperosmotic conditions even in the absence of glucose. Its rate of ox idation, in the presence or absence of any of ten other amino acids te sted, is strongly inhibited by hyperosmolality. Glucose oxidation is a lso inhibited by hyperosmolality, but to a lesser extent than that of alanine, and is inhibited by alanine, glutamate, and aspartate. Hypero smolality also inhibits the incorporation of label from 2-C-14acetat e into the putative storage carbohydrate, mannan, which occurs via the glyoxylate bypass and the as yet unexplored ''mannoneogenic'' pathway . The rates of glycolysis and of oxidation of several amino acids decr ease with increasing culture age, but the capacity to oxidize fatty ac ids increases, and in cells from 3-day stationary phase cultures hyper osmolality enhances rather than inhibits alanine oxidation.