Aconitate dehydratase

L-glutamic acid C. melassecola C. melassecola Glu A, citrate dehydrogenase, ppc, aconitate dehydratase ... 

A powerful competitive inhibitor (highly toxic) of aconitate dehydratase is fluorocitrate, an analogue of citrate ... 

Aconitate dehydratase, succinate dehydrogenase, and fumarase yield stereospecific products. Labeling experiments with in methyl and carboxyl carbons of acetyl-CoA or in all of the carbons of oxaloacetate yield the following results in terms of the intermediates or product formed. 

Aconitase is the trivial name for citrate dehydratase cw-aconitate hydratase (EC 4.2.1.3). It catalyzes the reversible isomerization reaction of citrate into isocitrate via the intermediate cA-aconitate (Figure 2). It is a water-soluble, monomeric protein. In eukaryotic cells aconitase is located in the mitochondrial matrix. In prokaryotes the enzyme occurs in the cytoplasma. The pig heart enzyme consists of 754 amino-acid residues, providing a molecular mass of 83 kDa [27], Aconitase from other sources has similar size. The porcine protein is synthesized with a mitochondrial targeting sequence. The mature, functional protein can be (over)expressed in Escherichia coli [28],... 

In this reaction, the tertiary alcoholic group of citrate is converted to a secondary alcoholic group that is more readily oxidized. The isomerization catalyzed by aconi-tate dehydratase (or aconitase) occurs by removal and addition of water with the formation of an intermediate, c -aconitate ... 

Other C-0 lyase enzymes include aconitate hydratase or aconitase (E. C. 4.2.1.3), an enzyme that catalyzes two tricarboxylic acid cycle steps from isocitric acid to citrate (14)1141 or vice versa, via the intermediate cis-aconitate (13). Citrate dehydratase (E. C. 4.2.1.4) is only capable of converting citrate to cis-aconitate and does not act on isocitrate (15) 115l... 

A similar reaction is catalyzed by homoaconitate hydratase (E.C. 4.2.1.36), which is an enzyme from the L-lysine synthesis that forms homocitric acid (2-hydrox-ybutane-l,2,4-tricarboxylic acid, 17) from homo-ris-aconitate (16)The enzyme 2-methylcitrate dehydratase (E. C. 4.2.1.79) catalyzes the addition of water to (Z)-but-2-ene-l,2,3-tricarboxylic acid (18) to yield 2-methylcitric acid (2-hydroxybutane-... 

The cis elimination and addition of water observed in the reversible 3-dehydroquinate dehydratase reaction represents the first example of this type recorded in enzyme chemistry. It contrasts with the known tram addition of water to other similar afi unsaturated compounds such as m-aconitate and fumarate Hanson and Rose formulated the addition as taking place in two distinct steps. First addition of water (or hydroxide anion) to give the enol or enolate anion (28) followed by protonation of the enol at the a... 

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