Abstract
1. D, L-thyroxine (final concentration: 1×10-4M) activates succinoxidase activity of mouse liver homogenate with addition of exogeneous cytochrome c, only in medium of narrow pH range around 7.4. Such effect of the hormone is not remarkable in pH 7.0 and 7.9.
2. No effect is found on the enzyme system with addition of L-diiodotyrosine and L-tyrosine in the same molar concentration with thyroxine (1×10-4M) at all pH employed.
3. From the data of spectrophotometric observation in ultraviolet region, solubility of thyroxine decreases with sharp gradient from pH 9 to 7.
