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In vitro enzyme activation with calbindin‐D 28k , the vitamin D‐dependent 28 kDa calcium binding protein
Author(s) -
Reisner Peter D.,
Christakos Sylvia,
Vanaman Thomas C.
Publication year - 1992
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(92)80342-e
Subject(s) - calmodulin , calcium binding protein , chemistry , cyclic nucleotide phosphodiesterase , phosphodiesterase , enzyme , calcium , biochemistry , atpase , calbindin , binding protein , enzyme activator , microbiology and biotechnology , biology , gene , organic chemistry
Purified porcine erythrocyte membrane Ca 2+ ‐ATPase and 3′:5′‐cyclic nucleotide phosphodiesterase were stimulated in a dose‐dependent, saturable manner with the vitamin D‐dependent calcium binding protein from rat kidney, calbindin‐D 28k (CaBP‐D 28k ). The concentration of CaBP‐D 28k required for half‐maximal activation ( K 0.5 act.) of the Ca 2+ ‐ATPase was 28 nM compared to 2.2 nM for calmodulin (CaM), with maximal activation equivalent upon addition or either excess CaM or CaBP‐D 28k , 3′:5′‐Cyclic nucleotide phosphodiesterase (PDE) also showed equivalent maximum saturable activation by calbindin ( K 0.5 act. = 90 nM) or calmodulin ( K 0.5 act. = 1.2 nM). CaBP‐D 28k was shown to effectively compete with CaM‐Sepharose for PDE binding. Immunoprecipitation with CaBP‐D 28k antiserum completely inhibited calbindin‐mediated activation of PDE but had no effect on calmodulin's ability to activate PDE. While the physiological significance of these results remains to be established, they do suggest that CaBP‐D 28k can activate enzymes and may be a regulator of yet to be identified target enzymes in certain tissues.