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1. 1. The amino acid compositions of the skin collagens from Rana catesbiana larva and adult and from the skin and tail of Notophthalmus viridescens were determined. 2. 2. The melting temperatures of the collagens were found to be 27°C for the tadpole; 29·3° for the frog and 29·8° for the newt. 3. 3. Imino acid content correlated with the T m of newt collagen. The T m s of the anuran collagens did not correlate with imino acid content. 4. 4. Using two methods of analysis, no significant tryptophan was detected in the anuran collagens. Tryptophan equivalent to one residue per tropocollagen molecule was detectable in the urodele collagens.

1. 1. The enzyme adenosine deaminase (E.C. 3.5.4.4) was purified from a sea anemone, Metridium senile . 2. 2. The substrate specificity and kinetic properties were similar to the calf intestine enzyme. 3. 3. The apparent molecular weight by Sephadex gel filtration was 70,000 daltons. 4. 4. No aminophosphonic acids were detected as constituent amino acids in this protein.

The order of addition of magnesium and glucose 1-phosphate to the phosphoenzyme (monophosphate phase) and of magnesium and glucose 1,6-diphosphate to the dephosphoenzyme (diphosphate phase) was investigated via substrate-velocity and equilibrium-isotope exchange experiments. All pathways ordered in both phases of the reaction were ruled out leaving only pathways random in one or both phases of the reaction; indicative evidence suggests that the pathway is actually random in both phases. The variations in maximum velocity and in the Michaelis constant for magnesium are described as a function of pH; the maximum velocity in the forward reaction is independent of pH from 6.5 to 8.3 while the Michaelis constant for magnesium depends on the basic form of two groups with pKa values in the range of 7.0 to 8.5.