GH Family

The oxidation-elimination-Michael addition-reduction route for what is formally a nucleophilic displacement appears to be taken by one family of glycoside hydrolases, GH4. The enzymes are dependent on divalent metal ions, particularly Mn , and contain a molecule of tightly bound NAD . Uniquely for a glycohydrolase family, GH 4 contains both a- and p-glycosi-dases. 

A crystal structure of this enzyme showed that the NAD was ideally placed to remove a hydride from C3 to the proR (A) face of the NAD . The structure of a 6-phospho a-glucosidase from Bacillus subtilis revealed a very 

The structure of the yeast enzyme in complex with NAD and 2-deoxy-o-glucitol 6-( )-vinylhomophosphonate suggested that the carbonyl activation was achieved by hydrogen bonding to two lysines, 373 and 412 in the case of Cl and 369 and 489 in the case of the transient ketone at C5 certainly mutation of Lys369, 412 and 489 abolished activity. 

Lobry de Bruyn and W. Alberda van Ekenstein, Reel. Trav. Chim. Pays-Bas 1895, 14, 156, and succeeding papers in the same journal. 

Gallons, H. Kersters-Hilderson, O. Van Opstal and C. K. De Bruyne, Enzyme Micobiol. TechnoL, 1986, 8, 696. 

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The amino acid sequences of hCS-A, hCS-B, and hCS-V are shown in relation to GH in Figure 1. The sequence of hCS-V is predicted from the DNA coding sequence and apparentiy does not possess amino acids 8—55 relative to GH and the other hCS molecules. It is not certain whether hCS-V is expressed or what function it may have. Human CS-A and hCS-B share approximately 85% identity with GH and also possess the disulfide bonds between Cys 53—165 and Cys 182—189 which produce the long and short S—loops characteristic of the PRL/GH family. 

In the absence of structural data for many interesting glycosidases, comparison of their sequences has revealed important structural relationships and similarities of catalytic properties. The database CAZy (Carbohydrate-Active EnZymes) is a sequence-based collection of currently around 100 GH families (currently GH 1 to GH 117, with around 15 families deleted), which are further grouped in 14 clans. It provides family-typical structural and mechanistic details and has become an invaluable tool in GH research.98... 

E. Fabre, G. Joucia, C. Moulis, S. Edmond, G. Richard, G. Potocki-Veronese, P. Monsan, and M. Remaud-Simeon, Glucansucrases of GH family 70 What are the determinants of their specificities Biocatal Biotransform., 24 (2006) 137-145. 

The large size (between 155 and 200 kDa) of glucansucrases from the GH family 70 has been a challenge for crystallographers for many years, and only very recently... 

In addition to the synthesis of polysaccharides, the transglucosylation activity of GH family 13 amylosucrase from N. polysaccharea has been employed to modify amylo-polysaccharides, underlying the interest of this enzyme for the design of novel thickening agents, resistant starches, and original carbohydrate-based dendritic nanoparticles [73, 74]. 

GH Family Substrate(s) stereochemistry — 7 site conformation Acid Trajectory Base(s)... 

The short-chain dehydrogenases, originally so called because the linear sequences then available rarely exceeded 250 residues, use tyrosine as the acid-base. As longer sequences with the same fold have become available, the name is something of a misnomer and the M,. range is now 250-350 residues for the core structure.They have B-side (proS) stereospecilicity for the coenzyme, which they bind in the syn conformation. Structurally, they adopt the same protein fold, much like a GH family, even though the degree of... 

The retaining enzymes, as GH family 27 members, act via a doubledisplacement mechanism, wherein one of the catalytic carboxylate group... 

A GH family 8 reducing-end xylose-releasing exooligoxylanase gene has also been expressed from this oiganism (BH2105) and was found to have a pH optimum of 6.2 to 7.3... 

The CAZy classification scheme complements the EC system by providing a protein sequence based framework within which the tremendous wealth of biochemical, mechanistic, and structural information on these enzymes can be united. In particular, the CAZy classification highlights evolutionary relationships between CAZymes, which in turn allow structural and functional relationships to be delineated within and between families. For example, although structural representatives exist for nearly three fourths of the more than 110 GH families, these consist of comparatively few three-dimensional fold types (13,29,30). In turn, catalytic activity can be related to enzyme structure within CAZy Whereas EC 3.2.1.21 describes all enzymes which have converged to become yS-glucosidases, the CAZy database highlights that this activity has been found in enzymes from three separate Families (GHl, GH3, and GH9), each with distinct three-dimensional protein folds employing one of two different catalytic mechanisms (29). 

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