Nitrogen metabolism during synchronous growth of chlorella. II. Free‐, peptide‐, and protein‐amino acid distribution

The levels of free‐, peptide‐, and protein‐amino acids were measured during the synchronous growth and division cycle of a thermophilic strain of Chlorella pyrenoidosa . Most of the protein amino acids exhibited little periodism (as % of total cellular‐N); however, the free‐ and peptide‐amino acids showed a variety of dramatic changes in level during the cell cycle. Fractionation of the acid‐soluble peptides by Sephadex gel‐filtration showed that an average of only 2.8% of the peptide amino acids were associated with peptides of high molecular weight (> 5000), while approximately 75% of the peptide amino acids were components of low molecular weight peptides (< 700). The low molecular weight peptides were predominately made up of relatively few amino acids (i.e., alanine, glutamate, lysine, glycine and arginine accounted for approximately 92% of the low molecular weight peptide amino acids). Several experiments revealed that nucleotide‐peptides do not contribute significantly to the pool of acid‐soluble peptides during the cell cycle of this organism.