Amino Acids

, Volume 31, Issue 2, pp 173–210

Acetohydroxyacid synthase and its role in the biosynthetic pathway for branched-chain amino acids

  • J. A. McCourt
  • R. G. Duggleby
Review Article

DOI: 10.1007/s00726-005-0297-3

Cite this article as:
McCourt, J. & Duggleby, R. Amino Acids (2006) 31: 173. doi:10.1007/s00726-005-0297-3

Summary.

The branched-chain amino acids are synthesized by plants, fungi and microorganisms, but not by animals. Therefore, the enzymes of this pathway are potential target sites for the development of antifungal agents, antimicrobials and herbicides. Most research has focused upon the first enzyme in this biosynthetic pathway, acetohydroxyacid synthase (AHAS) largely because it is the target site for many commercial herbicides. In this review we provide a brief overview of the important properties of each enzyme within the pathway and a detailed summary of the most recent AHAS research, against the perspective of work that has been carried out over the past 50 years.

Keywords: Acetohydroxyacid synthase – Acetolactate synthase – Branched-chain amino acids – Thiamin diphosphate – Flavin adenine dinucleotide – Herbicide – Inhibitor – Mechanism – Protein structure 

Abbreviations:

2-IPMS

2-isopropylmalate synthase

2-KB

2-ketobutyrate

3-IPMD

3-isopropylmalate dehydratase

3-IPMDH

3-isopropylmalate dehydrogenase

3-IPMI

3-isopropylmalate isomerase

Ac-ThDP

acetyl-ThDP

ADP

adenosine diphosphate

AHAS

acetohydroxyacid synthase

AHB

2-aceto-2-hydroxybutyrate

AL

2-acetolactate

ALS

acetolactate synthase

AMP

adenosine monophosphate

ATP

adenosine triphosphate

BCAA

branched-chain amino acid

BCAT

branched-chain aminotransferase

CE

chlorimuron ethyl

CoA

coenzyme A

CS

chlorsulfuron

CSU

catalytic subunit

DHAD

dihydroxyacid dehydratase

EDTA

ethylenediaminetetraacetic acid

FAD

flavin adenine dinucleotide

FADH2

reduced FAD

HE-ThDP

hydroxyethyl-ThDP (carbanion)

Hoe 704

2-dimethylphosphinoyl-2-hydroxyacetic acid

IP

imazapyr

IpOHA

N-hydroxy-N-isopropyloxamate

IQ

imazaquin

IT

imazethapyr

KARI

ketol-acid reductoisomerase

L-ThDP

lactyl-ThDP

MM

metsulfuron methyl

NAD(P)+

oxidized nicotinamide adenine dinucleotide (phosphate)

NAD(P)H

reduced nicotinamide adenine dinucleotide (phosphate)

O-IbOHA

O-isobutenyl oxalylhydroxamate

PAC

(R)-phenylacetyl carbinol

PDB

Protein Databank

PDC

pyruvate decarboxylase

POX

pyruvate oxidase

RSU

regulatory subunit

SM

sulfometuron methyl

TA

transaminase

TB

tribenuron methyl

TD

threonine deaminase

ThDP

thiamin diphosphate

TK

transketolase

TThDP

thiamin thiazolone diphosphate

U/mg

µmol product produced per minute per mg

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  • J. A. McCourt
    • 1
  • R. G. Duggleby
    • 1
  1. 1.School of Molecular and Microbial Sciences, University of QueenslandBrisbaneAustralia

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