Changes in microsomal hemoprotein content and glucose 6-phosphatase activity during low-temperature acclimation of Tetrahymena pyriformis

AbstractTo examine the temperture-associated alterations in microsomal enzymes in an eukaryote, Tetrahymena cells were transferred from 39.5–15°C. The content of cytochrome b-560ms, a cytochrome similar to but not identical with liver microsomal cytochrome b5, was slightly increased within 2 h after temperature shift-down, then gradually decreased, and reached the cytochrome b-560ms level of the 15°C-isothermally grown cells within 10 h following the temperature-shift. Cytochrome P-450 was not detected in Tetrahymena microsomes. The presence of a co-binding hemoprotein with a main peak at 420 nm was, however, observed. The amount of this hemoprotein was unchanged for 2 h after cold-shift. Later, it increased gradually and reached the maximum level at 10 h. Glucose 6-phosphatase activity increased slightly at 10 h, when cell division had already been regained. We conclude that cytochrome b-560ms, which is linked to the desaturase, may be essential for short-term adaptation (2 h after shift), while the amount of co-binding hemoprotein and the activity of glucose 6-phosphatase would be associated with long-term adaptation (10 h after temperature shift) in Tetrahymena cells