Short-term Products of14C-acetate Assimilation byChlorella pyrenoidosain the Light

Abstract

The kinetics of ¹⁴C-2-acetate assimilation by Chlorella pyrenoidosa in the light were examined. Under aerobic conditions the primary product of acetate assimilation was succinic acid which, after ten seconds, contained over 60 per cent of the ¹⁴C incorporated by the cells. The percentage of the total ¹⁴C in succinate fell with time, while that in citrate and glutamate increased. After 1800 sec over 60 per cent of ¹⁴C was present in two compounds, glutamic acid and an unknown compound (X). Glucose-6-phosphate, fructose-6-phosphate, phosphoglyceric acid and phosphoenolpyruvic acid became labelled after 60 sec but together never contained more than one per cent of the total ¹⁴C incorporated. Under anaerobic conditions succinate was still the primary product of acetate assimilation, and the absence of carbon dioxide resulted in a decrease in ¹⁴C incorporation into compound X. The pattern of acetate assimilation in acetate grown and acetate adapted Chlorella was very similar to that in photo-autotrophically grown Chlorella. In the presence of 10^–6M DCMU, succinic acid was the primary product of acetate assimilation, but there was an early Incorporation of ¹⁴C into glutamate, aspartate, and malate. 4 ×10^–3M MFA did not effect the early incorporation of ¹⁴C into succinic acid, but resulted in accumulation of ¹⁴C in citrate and a decreased amount in glutamate and in compound X.