Role of pyridoxal phosphate in the B12 coenzyme-dependent D-α-lysine mutase reaction

Morley, Colin G.D.; Stadtman, Thressa C.

doi:10.1021/bi00754a019

Cited by 20 publications

(20 citation statements)

References 22 publications

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“…Interestingly, the lysine fermentation pathway contains two analogous enzymes: lysine 5,6-aminomutase (5,6-LAM), which is AdoCbl-dependent (6,7), and lysine 2,3-aminomutase (2,3-LAM), which is an S-adenosylmethionine (AdoMet or SAM)-dependent ironsulfur enzyme (8)(9)(10). Both enzymes require pyridoxal 5Ј-phosphate (PLP) (8,11) in addition to AdoCbl or AdoMet, and both catalyze a 1,2 amino group shift with concomitant H atom migration (Fig. 1A).…”

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confidence: 99%

A locking mechanism preventing radical damage in the absence of substrate, as revealed by the x-ray structure of lysine 5,6-aminomutase

Berkovitch

Behshad

Tang

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

105

109

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Lysine 5,6-aminomutase is an adenosylcobalamin and pyridoxal-5 -phosphate-dependent enzyme that catalyzes a 1,2 rearrangement of the terminal amino group of DL-lysine and of L-␤-lysine. We have solved the x-ray structure of a substrate-free form of lysine-5,6-aminomutase from Clostridium sticklandii. In this structure, a Rossmann domain covalently binds pyridoxal-5 -phosphate by means of lysine 144 and positions it into the putative active site of a neighboring triosephosphate isomerase barrel domain, while simultaneously positioning the other cofactor, adenosylcobalamin, Ϸ25 Å from the active site. In this mode of pyridoxal-5 -phosphate binding, the cofactor acts as an anchor, tethering the separate polypeptide chain of the Rossmann domain to the triosephosphate isomerase barrel domain. Upon substrate binding and transaldimination of the lysine-144 linkage, the Rossmann domain would be free to rotate and bring adenosylcobalamin, pyridoxal-5 -phosphate, and substrate into proximity. Thus, the structure embodies a locking mechanism to keep the adenosylcobalamin out of the active site and prevent radical generation in the absence of substrate.A denosylcobalamin (AdoCbl; coenzyme B 12 ) is nature's biochemical radical reservoir, capable of catalyzing challenging chemical reactions by way of H atom abstraction and the generation of free-radical intermediates (1-3). AdoCbldependent isomerases catalyze 1,2 shifts between an H atom and a functional group such as -OH, -NH 3 ϩ , -(CO)S-coenzyme A, or other carbon-based groups. The catalytic power of AdoCbl lies in the homolytic cleavage of its weak (Ϸ30 kcal͞mol) organometallic C-Co bond, formed between an octahedral Co(III) center with five N coordinations and a 5Ј-deoxyadenosyl (Ado) axial ligand. C-Co bond homolysis results in the transient formation of cob(II)alamin and 5Ј-deoxyadenosyl radical (Ado • ). Ado • abstracts an H atom from the substrate, forming a substrate radical and 5Ј-deoxyadenosine (AdoH). To close the catalytic cycle, substrate reabstracts the H atom from AdoH, and recombination of cob(II)alamin and Ado • accompanies product formation. Amazingly, the enzymatic rate of C-Co bond homolysis is enhanced by a factor of Ϸ10 12 over nonenzymatic homolysis (4, 5). AdoCbl-dependent isomerases are often present in catabolic pathways and can serve to rearrange the substrate's carbon skeleton and͞or functional groups for further degradation. One such pathway that operates in several bacterial species is the fermentation of lysine to yield acetate. Interestingly, the lysine fermentation pathway contains two analogous enzymes: lysine 5,6-aminomutase (5,6-LAM), which is AdoCbl-dependent (6, 7), and lysine 2,3-aminomutase (2,3-LAM), which is an S-adenosylmethionine (AdoMet or SAM)-dependent ironsulfur enzyme (8-10). Both enzymes require pyridoxal 5Ј-phosphate (PLP) (8, 11) in addition to AdoCbl or AdoMet, and both catalyze a 1,2 amino group shift with concomitant H atom migration (Fig. 1A). In 5,6-LAM, AdoCbl is the source of the transient Ado • , whereas, in 2,3-L...

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confidence: 99%

A locking mechanism preventing radical damage in the absence of substrate, as revealed by the x-ray structure of lysine 5,6-aminomutase

Berkovitch

Behshad

Tang

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

105

109

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“…The migrating amino group is believed to form a Schiff base with PLP (10). Like acyl-CoA mutases, the migration probably proceeds through a cyclic transition state (11).…”

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confidence: 99%

Cloning, Sequencing, Heterologous Expression, Purification, and Characterization of Adenosylcobalamin-dependentd-Ornithine Aminomutase from Clostridium sticklandii

Chen¹,

Wu²,

Lin³

et al. 2001

Journal of Biological Chemistry

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“…Nitration of the E l component (resolved of pyridoxal phosphate) with tetranitromethane also destroyed its activity in the 432 THRESSA C. STADTMAN D-lysine mutase assay but the reconstituted holo El component was unaffected by tetranitromethane, suggesting that pyridoxal phosphate protects the protein from inactivation (44). The effects of these reagents suggest that an essential tyrosine moiety of the El protein may have been modified by acetylation or nitration, which is the case with aspartate aminotransferase (45,46).…”

Section: A Purification and Some Properties Of The Mutasementioning

confidence: 99%

“…Treatment with 1 m M NH20H for 10 min followed by overnight dialysis against pH 9.2 bicarbonate buffer resolves the mutase complex of pyridoxal phosphate and renders the preparations completely dependent on added pyridoxal phosphate for catalytic activity (44). Pyridoxamine phosphate does not substitute for pyridoxal phosphate.…”

Section: B Cofactor Requirements For D~-lysine Mutase Activitymentioning

confidence: 99%

Lysine Metabolism by Clostridia

Stadtman¹

1973

Advances in Enzymology - And Related Areas of Molecular Biology

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Role of pyridoxal phosphate in the B12 coenzyme-dependent D-α-lysine mutase reaction

Cited by 20 publications

References 22 publications

A locking mechanism preventing radical damage in the absence of substrate, as revealed by the x-ray structure of lysine 5,6-aminomutase

A locking mechanism preventing radical damage in the absence of substrate, as revealed by the x-ray structure of lysine 5,6-aminomutase

Cloning, Sequencing, Heterologous Expression, Purification, and Characterization of Adenosylcobalamin-dependentd-Ornithine Aminomutase from Clostridium sticklandii

Lysine Metabolism by Clostridia

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