Characterization of 2′:3′‐Cyclic Nucleotide 3′‐Phosphodiesterase: Rapid Isolation, Native Enzyme Analysis, Identification of a Serum‐Soluble Activity, and Kinetics

Abstract
The enzyme 2'':3''-cyclic nucleotide 3''-phosphodiesterase (CNPase) was isolated from bovine brain white matter by a rapid (72 h) procedure. The minimum MW of the enzyme was approximately 52,500 as estimated by sucrose density gradient analysis. When this isolated enzyme was stimulated with bovine serum albumin, the peak of activity was shifted to approximately 90,000 MW. Prior treatment by trypsin blocked the expression of the higher MW form of CNPase, but not the BSA activation of the enzyme. If the trypsin digestion was allowed to progress, the MW was gradually lowered to a broad peak sedimenting between 20,000-50,000 MW. An apparently soluble form of CNPase found in serum is described. Kinetic and MW comparisons between the serum soluble enzyme and CNPase isolated from bovine brain, and an analysis of substrate specificity, were made. The 2 enzymes are apparently identical.

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