MetaCyc Enzyme: [(S)-acetoin forming]-diacetyl reductase [multifunctional]

Gene: budC Accession Number: G-6713 (MetaCyc)

Species: Klebsiella pneumoniae

Subunit composition of [(S)-acetoin forming]-diacetyl reductase [multifunctional] = [BudC]4
         acetoin reductase subunit = BudC

General Background

There are two stereo-isomeric forms of acetoin - (R)-acetoin and (S)-acetoin, and three forms of 2,3-butanediol - (R,R)-2,3-butanediol, (S,S)-2,3-butanediol and (R,S)-2,3-butanediol.

Acetoin reductase (AR, also known as 2,3-butanediol dehydrogenase, or BDH) catalyzes a reversible reaction between acetoin and 2,3-butanediol. In addition, the enzyme usually catalyzes the non-reversible conversion of diacetyl to acetoin. Four types of AR activites have been described, differing in their stereo-specificity for both the substrate and the product:

1. An (R,S)-2,3-butanediol-forming R-acetoin reductase

2. An (R,S)-2,3-butanediol-forming S-acetoin reductase

3. An (S,S)-2,3-butanediol-forming S-acetoin reductase

4. An (R,R)-2,3-butanediol-forming R-acetoin reductase.

Among the enzymes that have been characteized, some appear to have only one of these activities, while others have multiple activities [Ui84].

About This Enzyme

The budC gene of Klebsiella pneumoniae was cloned and expressed in Escherichia coli, and shown to catalyze the reversible formation of (R)-acetoin from (R,S)-2,3-butanediol, as well as the production of (S)-acetoin from diacetyl [Ui97]. While the enzyme was stereoselective, it was also shown that when controlled by an IPTG-induced promoter and overexpressed in Escherichia coli, the enzyme lost its specificity and could produce (S,S)-2,3-butanediol from (S)-acetoin [Ui99].

This enzyme was also cloned and expressed in Clostridium acetobutylicum in an effort to construct a 2,3-butanediol over-producing strain [Wardwell01]. However, while the enzyme was successfully expressed and was able to convert portions of a racemic mixture of commercial acetoin added to the medium, it was not able to convert the acetoin produced by the host to 2,3-butanediol. The authors suggested that Clostridium acetobutylicum may produce (S)-acetoin, which is not a substrate for the Klebsiella pneumoniae enzyme [Wardwell01].

In a subsequent study, the enzyme was introduced into Escherichia coli for its diacetyl reductase activity, along with the (S)-acetoin reductase from Corynebacterium glutamicum, which converts (S)-acetoin to (S,S)-2,3-butanediol [Ui04]. This effort was successful, with 73% of the diacetyl added to the medium converted to (S,S)-2,3-butanediol.

The crystal srtructure has been obtained at 1.7 Å [Otagiri01].

Molecular Weight of Polypeptide: 26.642 kD (from nucleotide sequence), 31 kD (experimental) [Wardwell01 ]

Molecular Weight of Multimer: 96 kD (experimental)

pI: 4.8 [Wardwell01]

Unification Links: ModBase:Q48436 , Protein Model Portal:Q48436 , SMR:Q48436 , Swiss-Model:Q48436 , UniProt:Q48436

Relationship Links: Entrez-Nucleotide:PART-OF:AF098800 , Entrez-Nucleotide:PART-OF:D86412 , InterPro:IN-FAMILY:IPR002198 , InterPro:IN-FAMILY:IPR002347 , InterPro:IN-FAMILY:IPR014007 , InterPro:IN-FAMILY:IPR016040 , InterPro:IN-FAMILY:IPR020904 , PDB:Structure:1GEG , Pfam:IN-FAMILY:PF00106 , Prints:IN-FAMILY:PR00080 , Prints:IN-FAMILY:PR00081 , Prosite:IN-FAMILY:PS00061

Gene-Reaction Schematic: ?

Gene-Reaction Schematic

MultiFun Terms: metabolism carbon utilization carbon compounds

Revised 23-Nov-2009 by Caspi R , SRI International

Enzymatic reaction of: [(S)-acetoin forming]-diacetyl reductase

EC Number:

diacetyl + NADH + H+ <=> (S)-acetoin + NAD+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.

The reaction is irreversible in the direction shown.

In Pathways: superpathway of 2,3-butanediol biosynthesis , (S)-acetoin biosynthesis

pH(opt): 5.5 [Ui97]

Enzymatic reaction of: [(R)-acetoin forming]-meso-2,3-butanediol dehydrogenase

EC Number: 1.1.1.-

(R,S)-2,3-butanediol + NAD+ <=> (R)-acetoin + NADH + H+

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction of enzyme catalysis.

This reaction is reversible.

In Pathways: superpathway of 2,3-butanediol biosynthesis , meso-butanediol biosynthesis I

Kinetic Parameters:

Km (μM)

pH(opt): 5.5 [Ui97]


Otagiri01: Otagiri M, Kurisu G, Ui S, Takusagawa Y, Ohkuma M, Kudo T, Kusunoki M (2001). "Crystal structure of meso-2,3-butanediol dehydrogenase in a complex with NAD+ and inhibitor mercaptoethanol at 1.7 A resolution for understanding of chiral substrate recognition mechanisms." J Biochem 129(2);205-8. PMID: 11173520

Ui04: Ui S, Takusagawa Y, Sato T, Ohtsuki T, Mimura A, Ohkuma M, Kudo T (2004). "Production of L-2,3-butanediol by a new pathway constructed in Escherichia coli." Lett Appl Microbiol 39(6);533-7. PMID: 15548307

Ui84: Ui, S., Matsuyama, N., Masuda, H., Muraki, H. (1984). "Mechanism for the formation of 2,3-butanediol stereoisomers in Klebsiella pneumoniae." J. Ferment. Technol. 62: 551-559.

Ui97: Ui, S., Okajima, Y., Mimura, A., Kanai, H., Kobayashi, T., Kudo, T. (1997). "Sequence analysis of the gene for and characterization of D-acetoin forming meso-2,3-butanediol dehydrogenase of Klebsiella pneumoniae expressed in Escherichia coli." J. Ferment. Bioeng. 83: 32-37.

Ui99: Ui S, Mimura A, Ohkuma M, Kudo T (1999). "Formation of a chiral acetoinic compound from diacetyl by Escherichia coli expressing meso-2,3-butanediol dehydrogenase." Lett Appl Microbiol 28(6);457-60. PMID: 10389264

Wardwell01: Wardwell SA, Yang YT, Chang HY, San KY, Rudolph FB, Bennett GN (2001). "Expression of the Klebsiella pneumoniae CG21 acetoin reductase gene in Clostridium acetobutylicum ATCC 824." J Ind Microbiol Biotechnol 27(4);220-7. PMID: 11687934

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
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