Tyrosine aminotransferase activity of frog (Rana esculenta) liver—III. A circannual study

Abstract 1. 1. A circannual study of tyrosine aminotransferase and other metabolic enzymes in frog liver is reported. The subcellular distribution of all enzymatic activities under investigation was also studied. 2. 2. Results show significant oscillations of all enzymatic activities throughout the year; in particular tyrosine aminotransferase has a marked summer maximum. 3. 3. The subcellular distribution of tyrosine aminotransferase shows significant variations: the soluble activity of the enzyme presents a bimodal circannual distribution, which has its counterpart in an increased activity of heavier fractions.