Transcarboxylase 5S structures: assembly and catalytic mechanism of a multienzyme complex subunit

Carbon dioxide is fundamental to the physiology of all organisms. There is considerable interest in the precise molecular mechanisms that organisms use to directly sense CO 2 . Here we demonstrate that a mammalian recombinant G-protein-activated adenylyl cyclase and the related Rv1625c adenylyl cyclase of Mycobacterium tuberculosis are specifically stimulated by CO 2 . Stimulation occurred at physiological concentrations of CO 2 through increased k cat . CO 2 increased the affinity of enzyme for metal co-factor, but contact with metal was not necessary as CO 2 interacted directly with apoenzyme. CO 2 stimulated the activity of both G-protein-regulated adenylyl cyclases and Rv1625c in vivo. Activation of G-protein regulated adenylyl cyclases by CO 2 gave a corresponding increase in cAMP-response element-binding protein (CREB) phosphorylation. Comparison of the responses of the G-protein regulated adenylyl cyclases and the molecularly, and biochemically distinct mammalian soluble adenylyl cyclase revealed that whereas G-protein-regulated enzymes are responsive to CO 2 , the soluble adenylyl cyclase is responsive to both CO 2 and bicarbonate ion. We have, thus, identified a signaling enzyme by which eukaryotes can directly detect and respond to fluctuating CO 2 .

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“…Refs. [43][44][45]. It is also possible that changes in the local environment may permit arginine to participate in a CO 2 binding site (46).…”

Section: Resultsmentioning

confidence: 99%

Stimulation of Mammalian G-protein-responsive Adenylyl Cyclases by Carbon Dioxide

Townsend

Holliday

Fenyk

et al. 2009

Journal of Biological Chemistry

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“…droxy-2-methylglutaryl-CoA lyase (10), 2-phosphinomethylmalate synthase (22,41,52), and pyruvate carboxytransferase 5S (19). These proteins all appear to be TIM barrel metalloenzymes and thus structurally quite different from Si-citrate synthase (39).…”

Section: Discussionmentioning

confidence: 99%

Re -Citrate Synthase from Clostridium kluyveri Is Phylogenetically Related to Homocitrate Synthase and Isopropylmalate Synthase Rather Than to Si -Citrate Synthase

Hagemeier

Seedorf

et al. 2007

J Bacteriol

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The synthesis of citrate from acetyl-coenzyme A and oxaloacetate is catalyzed in most organisms by a Si-citrate synthase, which is Si-face stereospecific with respect to C-2 of oxaloacetate. However, in Clostridium kluyveri and some other strictly anaerobic bacteria, the reaction is catalyzed by a Re-citrate synthase, whose primary structure has remained elusive. We report here that Re-citrate synthase from C. kluyveri is the product of a gene predicted to encode isopropylmalate synthase. C. kluyveri is also shown to contain a gene for Si-citrate synthase, which explains why cell extracts of the organism always exhibit some Si-citrate synthase activity.

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“…As such the exact mechanism by which the keto acid enolate is stabilized is unclear at the present time. 10,20,21,91,92 It is possible that stabilization of the keto acid enolate is achieved through a combination of metal ion coordination and/or interaction with an Arg/Gln side chain pair. It is also possible that these enzymes stabilize the biotin enolate through tetrahedral coordination of the ureido oxygen.…”

Section: Carboxyltransferase Domains Without a Crotonase Foldmentioning

confidence: 99%

The enzymes of biotin dependent CO₂ metabolism: What structures reveal about their reaction mechanisms

2012

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Biotin is the major cofactor involved in carbon dioxide metabolism. Indeed, biotindependent enzymes are ubiquitous in nature and are involved in a myriad of metabolic processes including fatty acid synthesis and gluconeogenesis. The cofactor, itself, is composed of a ureido ring, a tetrahydrothiophene ring, and a valeric acid side chain. It is the ureido ring that functions as the CO 2 carrier. A complete understanding of biotin-dependent enzymes is critically important for translational research in light of the fact that some of these enzymes serve as targets for antiobesity agents, antibiotics, and herbicides. Prior to 1990, however, there was a dearth of information regarding the molecular architectures of biotin-dependent enzymes. In recent years there has been an explosion in the number of three-dimensional structures reported for these proteins. Here we review our current understanding of the structures and functions of biotindependent enzymes. In addition, we provide a critical analysis of what these structures have and have not revealed about biotin-dependent catalysis.

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Transcarboxylase 5S structures: assembly and catalytic mechanism of a multienzyme complex subunit

Cited by 40 publications

References 70 publications

Stimulation of Mammalian G-protein-responsive Adenylyl Cyclases by Carbon Dioxide

Stimulation of Mammalian G-protein-responsive Adenylyl Cyclases by Carbon Dioxide

Re -Citrate Synthase from Clostridium kluyveri Is Phylogenetically Related to Homocitrate Synthase and Isopropylmalate Synthase Rather Than to Si -Citrate Synthase

The enzymes of biotin dependent CO₂ metabolism: What structures reveal about their reaction mechanisms

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Transcarboxylase 5S structures: assembly and catalytic mechanism of a multienzyme complex subunit

Cited by 40 publications

References 70 publications

Stimulation of Mammalian G-protein-responsive Adenylyl Cyclases by Carbon Dioxide

Stimulation of Mammalian G-protein-responsive Adenylyl Cyclases by Carbon Dioxide

Re -Citrate Synthase from Clostridium kluyveri Is Phylogenetically Related to Homocitrate Synthase and Isopropylmalate Synthase Rather Than to Si -Citrate Synthase

The enzymes of biotin dependent CO2 metabolism: What structures reveal about their reaction mechanisms

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The enzymes of biotin dependent CO₂ metabolism: What structures reveal about their reaction mechanisms