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Lysosomal glycerophosphocholine phosphodiesterase in Tetrahymena
Author(s) -
FlorinChristensen J.,
FlorinChristensen M.
Publication year - 1999
Publication title -
iubmb life
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.132
H-Index - 113
eISSN - 1521-6551
pISSN - 1521-6543
DOI - 10.1080/15216549900201303
Subject(s) - tetrahymena , biochemistry , phosphatidylcholine , extracellular , phosphodiesterase , biology , polyacrylamide gel electrophoresis , acid phosphatase , enzyme , gel electrophoresis , chemistry , phospholipid , membrane
The purification and characterization of a novel phosphodiesterase (PDE) is presented. The activity was detected in the extracellular medium of Tetrahymena thermophila cultures, by the release of p‐nitrophenol from p‐nitrophenylphosphocholine (PNPPC) with an acidic pH optimum: In cell homogenates, it is sedimentable, shows a latency similar to that of acid phosphatase and is co‐secreted with this enzyme, indicating that it is a lysosomal hydrolase. PNPPC‐PDE was purified to homogeneity from the extracellular medium, yielding a single band of 58 kD on SDS polyacrylamide gel electrophoresis. It catalyzed the release of glycerol from glycerophosphocholine (GPC) and GPC competitively inhibits degradation of PNPPC. We present further evidence indicating that the natural substrate for PNPPC‐PDE is GPC. Thus, Tetrahymena becomes the first eukaryote in which a lysosomal GPC‐PDE is observed. This finding provides a new pathway for the complete breakdown of phosphatidylcholine in a lysosomal medium.