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Arch Biochem Biophys. 2011 Apr 1;508(1):25-30. doi: 10.1016/ Epub 2011 Jan 22.

Purification and characterization of cystathionine β-synthase bearing a cobalt protoporphyrin.

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  • 1Department of Pediatrics and the Colorado Intellectual and Developmental Disabilities Research Center (IDDRC), University of Colorado at Denver, 12800 E 19th Ave., Aurora, CO 80045, USA.


Human cystathionine β-synthase (CBS), a pivotal enzyme in the metabolism of homocysteine, is a pyridoxal-5'-phosphate-dependent enzyme that also contains heme, a second cofactor whose function is still unclear. One strategy for elucidation of heme function is its replacement with different metalloporphyrins or with porphyrins containing different substituent groups. This paper describes a novel expression approach and purification of cobalt CBS (CoCBS), which results in a high yield of fully active, high purity enzyme, in which heme is substituted by Co-protoporphyrin IX (CoPPIX). Metal content analysis showed that the enzyme contained 92% cobalt and 8% iron. CoCBS was indistinguishable from wild-type FeCBS in its activity, tetrameric oligomerization, PLP saturation and responsiveness to the allosteric activator, S-adenosyl-l-methionine. The observed biochemical and spectral characteristics of CoCBS provide further support for the suggestion that heme is involved in structural integrity and folding of this unusual enzyme.

Copyright © 2011 Elsevier Inc. All rights reserved.

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