Floridean starch metabolism of Porphyridium purpureum (Rhodophyta). II. Changes during the cell cycle

Abstract

Abstract Exponential phase-cells of Porphyridium purpureum initiated cell division within the last 2 h of the light period in a 12: 12 h photoregime. Cell concentration increased by a factor of 2 · 5 over a period of 6 h. Starch per ml culture, that is regardless of cell division, increased linearly throughout the light phase but declined slightly during the subsequent dark period. Cellular starch contents also rose during the light phase until the beginning of cell division, after which levels decreased to those present at the commencement of the cell cycle. The activities per ml culture of two potential starch forming enzymes, phosphorylase and ADPG transferase, increased during the light period by a factor of 2 · 5 to 3 · 0, thereby keeping pace with the rate of cell division. During the following dark phase, phosphorylase activity remained constant whereas that of transferase declined slightly. Cellular activities of these two enzymes also rose during the light period until the initiation of cell divi...