ADAPTATION OF METABOLIC ENZYME-ACTIVITIES OF TRYPANOSOMA-BRUCEI PROMASTIGOTES TO GROWTH-RATE AND CARBON REGIMEN

The insect stage of Trypanosoma brucei adapted the activities of 16 me tabolic enzymes to growth rate and carbon source. Cells were grown in chemostats,vith glucose, rate limiting or in excess, or high concentra tions of proline as carbon and energy sources. At each steady state, s amples were collected for measurements of substrate and end product co ncentrations, cellular parameters, and enzyme activities. Correlation coefficients were calculated for all parameters and used to analyze th e data set, Rates of substrate consumption and end product formation i ncreased with increasing growth rate. Acetate and succinate were the m ajor nonvolatile end products, but measurable quantities of alanine we re also produced. More acetate than succinate was formed during growth on glucose, but growth on proline yielded an equimolar ratio. Growth rate barely affected the relative amounts of end products formed, The end products accounted for the glucose consumed during glucose-limited growth and growth at high rates on excess glucose. A discrepancy, ind icating production of CO2, occurred during slow growth on excess gluco se and, even more pronounced, in tells growing on proline, The activit ies of the metabolic enzymes varied by factors of 2 to 40. There was n o single enzyme that correlated with consumption of substrate and/or e nd product formation in all eases, A group of enzymes whose activities rigorously covaried could also not be identified. These findings indi cate that T. brucei adapted the activities of each of the metabolic en zymes studied separately. The results of this complex manner of adapta tion were more or less constant ratios of the end products and a very efficient energy metabolism.