Extracellular phosphatases of Chlamydomonas reinhardi and their regulation

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Abstract
C. reinhardi, cultured under normal growth conditions, secreted significant amounts of protein and carbohydrates but not lipids or nucleic acids. A 5-fold increase in light intensity led to a 10-fold increase in secreted protein and carbohydrate. Among the proteins secreted was acid phosphatase with a pH optimum at 4.8 like the enzyme in the cells. P-depleted algae grown on minimal orthophosphate contained and secreted both acid and alkaline phosphatase. The pH optimum of the intracellular alkaline phosphatase was 9.2. When P-depleted cells were grown with increasing orthophosphate, intra- and extracellular alkaline phosphatase was almost completely repressed and intra- and extracellular acid phosphatase was partially repressed. Extracellular acid and alkaline phosphatase increased with the age of culture. Electrophoresis indicated only 1 acid and 1 alkaline phosphatase in phosphorus-satisfied and P-depleted cells. Chlamydomonas cells suspended in an inorganic salt solution secreted only acid phosphatase; the absence of any extracellular cytoplasmic marker enzyme indicated that there was little, if any, autolysis to account for the extracellular acid enzyme. P-depleted cells grew on organic phosphates as the sole source of orthophosphate. Ribose-5-phosphate was best for cell multiplication, and its utility was due to the cell''s ability to use the ribose as well as the orthophosphatase for cell multiplication.