Methylglutaconyl hydratase

Serine dehydratase Enoyl-CoA hydratase Methylglutaconyl-CoA hydratase Cystathionine p-synthase [PLP]... 

Methylglutaryl-CoA hydratase (EC 4.2.1.18) catalyzes the reversible dehydration of HMG-CoA into 3-methylglutaconyl-CoA and is known from mammalian cells to be involved in leucine metabolism. This enzyme was detected in C. roseus suspension cultured cells and partially purified (87). Further enzymes channeling HMG-CoA away from isoprenoid biosynthesis in C. roseus cells were detected by a selective HPLC system showing that the CoA-esters may be rapidly dephosphorylated on the 3 -position by the action of 3 -nucleotidases (87). 

Methylglutaconyl-CoA (MG-CoA) hydratase (EC 4.2.1.18) activity yields MG-CoA from the substrate HMG-CoA. As for HMG-CoA lyase, this enzyme may compete with terpenoid biosynthesis. In mammalian cells this enzyme is involved in leucine metabolism. The activity of the enzyme was detected in various plant cell cultures, among others Arabidopsis thaliana. The C. roseus enzyme was partially purified by ammonium sulfate precipitation, ion- exchange and hydrcxyapatite chromatography, and gel filtration [5]. It is relatively stable and does not require cofactors. 

The inborn errors of L-leucine catabolism present biochemically with branched-chain amino and/or organic aciduria [1]. These disorders include maple syrup disease (MSD branched-chain a-ketoacid dehydrogenase (BCKD) deficiency), isovaleric acidemia (isovaleryl-coenzyme A (CoA) dehydrogenase deficiency), isolated 3-methylcrotonyl-CoA carboxylase deficiency, the 3-methylglutaconic acidurias (3-methylglutaconyl-CoA hydratase deficiency, Barth syndrome, and other disorders in which the primary defect has not been demonstrated), and 3-hydroxy-3-methylglutaric aciduria (3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase deficiency). 

Methylglutaconk aciduria type I (3"methylglutaconyl-CoA hydratase deficiency) WBC, FB 250950... 

Table 6.5. Barth syndrome (Xdinked 3-methylglutaconk aciduria, normal 3-methylglutaconyl-CoA hydratase activity) ...

There have been two reports concerning three patients with 3-methylglutaconic aciduria with proposed deficiency of 3-methylglutaconyl-CoA hydratase, which normally hydrates the unsaturated acid to 3-hydroxy-3-methylglutaryl-CoA. 

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