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Since phosphodiesterase is widely used for establishing nucleotide sequence, the properties of its possible contaminants deserve study. A nuclease of the venom of Bothrops atrox has been purified approximately 1000-fold from the 42y0 acetone precipitate, which is a by-product of the preparation of venom phosphodiesterase. The preparation of enzyme thus obtained can split both ribo-and deoxyribonucleic acids a t a similar rate. The enzyme has an optimal activity at pH 5.0 and requires no magnesium. It acts on DKA as an endonuclease, and produces predominantly tri-or higher oligonucleotides all of which terminate in 3'-monoesterified phosphate. At the early stages of digestion de-Gp-Gp' is the most susceptible bond. As the digestion progresses the specificity in respect to the adjacent bases decreases, and the length of the substrate chain becomes more significant. After an exhaustive digestion fragments are obtained in which all four bases in terminal positions occur in an almost random distribution.

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L-Asparaginase activity reaches maximal values at the stationary phase of growth of Tetrahymena pyriformis and fluctuates upon the growth conditions and the composition of the medium. Most of the L-asparaginase activity (80%) is associated with the endoplasmic reticulum, and the remaining with the pellicles. Detergents either alone or in combination with NaCl up to 0.5 M concentration failed to solubilize L-asparaginase. Solubilization can be accomplished by means of either the chaotropic agents KSCN and NaClO4, or 0.1 M sodium phosphate buffer pH 8.0, following pretreatment of the particulates with 2% w/v Triton X100. L-Asparaginase has been purified to near homogeneity by hydrophobic and gel filtration chromatography. The native enzyme has a relative molecular weight of 230,000. It is a multiple subunit enzyme, with subunit size of 39,000. Its isoelectric point is at pH 6.8. It acts optimally at pH 8.6 with a Km of 2.2 mM. It does not hydrolyse L-glutamine and its reaction is inhibited competitively by D-aspartic acid and D-asparagine as well as by L-asparagine analogues with substituents at the beta position.

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