Glycoside Hydrolase Family 57

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• Author: ^^^Stefan Janecek^^^
• Responsible Curator: ^^^Stefan Janecek^^^

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Glycoside Hydrolase Family GH57
Clan	not assigned yet
Mechanism	retaining
Active site residues	known/not known
CAZy DB link
http://www.cazy.org/fam/GH57.html

Substrate specificities

The family GH57 was established in 1996 (Henrissat & Bairoch 1996) based on the existence of the sequences of two “α-amylases” that were dissimilar to typical family GH13 α-amylases (MacGregor et al. 2001). The two were the heat-stable eubacterial amylase from Dictyoglomus thermophilum known from 1988 (Fukusumi et al. 1988) and the extremely thermostable archaeal amylase from Pyrococcus furiosus determined in 1993 (Laderman et al. 1993a).

The family has expanded mainly due to running genome sequencing projects. Nowadays it contains more than 400 members; all originating from prokaryotes (http://www.cazy.org/fam/GH57.html). With regard to the enzyme specificities, the family GH57 covers the α-amylase (EC 3.2.1.1), α-galactosidase (EC 3.2.1.22), amylopullulanase (EC 3.2.1.1/41), branching enzyme (EC 2.4.1.18) and 4-α-glucanotransferase (EC 2.4.1.25). It is worth mentioning that the two constituent members, i.e. the “α-amylases” from D. thermophilum and P. furiosus are rather the 4-α-glucanotransferases since the former was later proven to have the transglycosylating activity (Nakajima et al. 2004), whereas the latter was shown already in 1993 to exhibit the 4-α-glucanotransferase activity (Laderman et al., 1993b). And it is also of interest that the real enzymes form only about 5% of the family members. The vast majority of the GH57 are hypothetical proteins.

Kinetics and Mechanism

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Catalytic Residues

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Three-dimensional structures

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Family Firsts

First sterochemistry determination

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First catalytic nucleophile identification

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First general acid/base residue identification

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First 3-D structure

The first 3-D structure of a GH57 member was that of the 4-alpha-glucanotransferase from Thermococcus litoralis [1].

References

1. Imamura H, Fushinobu S, Yamamoto M, Kumasaka T, Jeon BS, Wakagi T, and Matsuzawa H. (2003). Crystal structures of 4-alpha-glucanotransferase from Thermococcus litoralis and its complex with an inhibitor. J Biol Chem. 2003;278(21):19378-86. DOI:10.1074/jbc.M213134200 |