Epimerase


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epimerase

[ə′pim·ə‚rās]
(biochemistry)
A type of enzyme that catalyzes the rearrangement of hydroxyl groups on a substrate.

Epimerase

 

any enzyme of the isomerase class that catalyzes the inversion of L- and D-isomers with several centers of asymmetry. For example, aldose 1-epimerase (a mutarotase) catalyzes the conversion of of α-D-glucose into β-D-glucose. Epimerases are widely found in nature. (SeeRACEMASE.)

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Anyhow, compelling evidence suggests that reduced DCIns levels are associated with impaired insulin transduction in insulin-sensitive tissues, where insulin-sensitive epimerase is unable to convert myoIns into DCIns.
In both galactokinase and epimerase deficiency, children are generally asymptomatic and experience few or no ill effects from lack of the particular enzyme.
The metabolism of galactose involves 3 enzymes of the Leloir pathway, galactokinase (GALK, EC 2.7.1.6), galactose-1-phosphate uridylyltransferase (GALT, EC2.7.7.12), (4) and uridine diphosphate galactose-4'epimerase (GALE, EC 5.1.3.2).
The paradox theory published and discussed by Nestler and Carlomagno [18, 19] suggests that D-Chiro Inositol in not physiological high dosages has a negative impact on the quality of oocytes of PCOS women, as the ovarian epimerase function is not altered in PCOS patients so that the myoinositol levels in the follicular fluids remain low if only D-Chiro-Inositol is supplemented.
We detected a wide heterozygous duplication at 2p13.3 that spanned about 735 kb and included 10 genes: CD207 (CD207 molecule, langerin), VAX2 (ventral anterior homeobox 2), ATP6V1B1 (ATPase, H+ transporting, lysosomal 56/58kDa, V1 subunitB1), ANKRD53 (ankyrin repeat domain 53), TEX261 (testis expressed 261), NAGK (N-acetylglucosamine kinase), MCEE (methylmalonyl CoA epimerase), MPHOSPH10 [M-phase phosphoprotein 10 (U3 small nucleolar ribonucleoprotein)], PAIP2B [poly(A) binding protein interacting protein 2B], and ZNF638 (zinc finger protein 638), as well as the first 20 exons of DYSF [dysferlin, limb girdle muscular dystrophy 2B (autosomal recessive)], which causes LGMD2B (33).
MI is then converted in DCI by epimerase in mammalian tissues.
Larner, "Decreased myoinositol to chiro-inositol (M/C) ratios and increased M/C epimerase activity in PCOS theca cells demonstrate increased insulin sensitivity compared to controls," Endocrine Journal, vol.
There is only evidence that both myo-inositol to chiro-inositol epimerase activities and chiro-inositol to myo-inositol ratios are decreased in tissues of GK type 2 diabetic rats, potentially playing a role in explaining the decreased chiro-inositol to myo-inositol urine and tissue ratios observed in animal and human studies [24].
Clinical 1 No clinical abnormality 2 FNA 3 FNA 4 FNA 5 Epimerase deficiency 6 Epimerase deficiency 7 Epimerase deficiency (mild) 8 FNA 9 FNA 10 FNA 11 Epimerase deficiency (profound) 12 Epimerase deficiency (transient) 13 Het D/G 14 Het D 15 Het D/G 16 Het D 17 Het D/G 18 Het D 19 No abnormality 20 FNA (a) To convert Gal concentrations to milligrams per deciliter, divide by 0.0555.
Patients with hIBM and DMRV (also known as Nonaka myopathy) have biallelic missense mutations in the epimerase and/or kinase domains of the GNE gene.
The Paigen and Beutler assays in combination are used by many screening laboratories (2) and can detect deficiencies in GALT, galactokinase, and galactose epimerase; however, these methods have relatively high false-positive rates (3).
Multiple posttranslational modifications occur in the Golgi complex, including the addition of disaccharides as well as epimerisation and sulfation of saccharide units, all performed by various glycosyltransferases, epimerases, and sulfotransferases [3].