10.1021\/bi011687i<\/a><\/p>\nAuthors:<\/h4>\n
Javier Seravalli, Manoj Kumar, Stephen W. Ragsdale<\/p>\n
Abstract:<\/h4>\n
CO dehydrogenase\/acetyl-CoA synthase (CODH\/ACS), a key enzyme in the Wood-Ljungdahl pathway of anaerobic CO(2) fixation, is a bifunctional enzyme containing CODH, which catalyzes the reversible two-electron oxidation of CO to CO(2), and ACS, which catalyzes acetyl-CoA synthesis from CoA, CO, and a methylated corrinoid iron-sulfur protein (CFeSP). ACS contains an active site nickel iron-sulfur cluster that forms a paramagnetic adduct with CO, called the nickel iron carbon (NiFeC) species, which we have hypothesized to be a key intermediate in acetyl-CoA synthesis. This hypothesis has been controversial. Here we report the results of steady-state kinetic experiments; stopped-flow and rapid freeze-quench transient kinetic studies; and kinetic simulations that directly test this hypothesis. Our results show that formation of the NiFeC intermediate occurs at approximately the same rate as, and its decay occurs 6-fold faster than, the rate of acetyl-CoA synthesis. Kinetic simulations of the steady-state and transient kinetic results accommodate the NiFeC species in the mechanism and define the rate constants for the elementary steps in acetyl-CoA synthesis. The combined results strongly support the kinetic competence of the NiFeC species in the Wood-Ljungdahl pathway. The results also imply that the methylation of ACS occurs by attack of the Ni(1+) site in the NiFeC intermediate on the methyl group of the methylated CFeSP. Our results indicate that CO inhibits acetyl-CoA synthesis by inhibiting this methyl transfer reaction. Under noninhibitory CO concentrations (below 100 microM), formation of the NiFeC species is rate-limiting, while at higher inhibitory CO concentrations, methyl transfer to ACS becomes rate-limiting.<\/p>\n","protected":false},"excerpt":{"rendered":"
DOI: 10.1021\/bi011687i Authors: Javier Seravalli, Manoj Kumar, Stephen W. Ragsdale Abstract: CO dehydrogenase\/acetyl-CoA synthase (CODH\/ACS), a key enzyme in the Wood-Ljungdahl pathway of anaerobic CO(2) fixation, is a bifunctional enzyme containing CODH, which catalyzes the reversible two-electron oxidation of CO to CO(2), and ACS, which catalyzes acetyl-CoA synthesis from CoA, CO, and a methylated corrinoid […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5],"tags":[],"class_list":["post-693","post","type-post","status-publish","format-standard","hentry","category-freeze-quench"],"_links":{"self":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts\/693","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=693"}],"version-history":[{"count":0,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=\/wp\/v2\/posts\/693\/revisions"}],"wp:attachment":[{"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=693"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=693"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/citations.tools.bio-logic.fr\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=693"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}