N-terminal catalytic domain of a thermoactive alpha-amylase from Methanococcus jannaschii and similar proteins; glycoside hydrolase family 57 (GH57). The subfamily is represented by a thermostable alpha-amylase (MJA1, EC 3.2.1.1) encoded from the hyperthermophilic archaeon Methanococcus jannaschii locus, M J1611. MJA1 has a broad pH optimum 5.0-8.0. It exhibits extremely thermophilic alpha-amylase activity that catalyzes the hydrolysis of large sugar polymers with alpha-l,6 and alpha-l,4 linkages, and yields products including glucose polymers of 1-7 units. MJ1611 also encodes another alpha-amylase with catalytic features distinct from MJA1, which belongs to glycoside hydrolase family 13 (GH-13), and is not included here. This subfamily also includes many uncharacterized proteins found in bacteria and archaea.

Glycosyl hydrolase family 57. This family includes alpha-amylase (EC:3.2.1.1), 4--glucanotransferase (EC:2.4.1.-) and amylopullulanase enzymes.

Alpha-amylase/alpha-mannosidase, GH57 family [Carbohydrate transport and metabolism].

N-terminal catalytic domain of heat stable retaining glycoside hydrolase family 57. Glycoside hydrolase family 57(GH57) is a chiefly prokaryotic family with the majority of thermostable enzymes coming from extremophiles (many of these are archaeal hyperthermophiles), which exhibit the enzyme specificities of alpha-amylase (EC 3.2.1.1), 4-alpha-glucanotransferase (EC 2.4.1.25), amylopullulanase (EC 3.2.1.1/41), and alpha-galactosidase (EC 3.2.1.22). This family also includes many hypothetical proteins with uncharacterized activity and specificity. GH57s cleave alpha-glycosidic bonds by employing a retaining mechanism, which involves a glycosyl-enzyme intermediate, allowing transglycosylation.

N-terminal catalytic domain of 4-alpha-glucanotransferase; glycoside hydrolase family 57 (GH57). 4-alpha-glucanotransferase (TLGT, EC 2.4.1.25) plays a key role in the maltose metabolism. It catalyzes the disproportionation of amylose and the formation of large cyclic alpha-1,4-glucan (cycloamylose) from linear amylose. TLGT functions as a homodimer. Each monomer is composed of two domains, an N-terminal catalytic domain with a (beta/alpha)7 barrel fold and a C-terminal domain with a twisted beta-sandwich fold. Some family members have been designated as alpha-amylases, such as the heat-stable eubacterial amylase from Dictyoglomus thermophilum (DtAmyA) and the extremely thermostable archaeal amylase from Pyrococcus furiosus(PfAmyA). However, both of these proteins are 4-alpha-glucanotransferases. DtAmyA was shown to have transglycosylating activity and PfAmyA exhibits 4-alpha-glucanotransferase activity.

Putative alpha-amylase OS=Methanocaldococcus jannaschii (strain ATCC 43067 / DSM 2661 / JAL-1 / JCM 10045 / NBRC 100440) OX=243232 GN=MJ1611 PE=3 SV=1

Alpha-amylase OS=Pyrococcus abyssi (strain GE5 / Orsay) OX=272844 GN=amyA PE=3 SV=1

Alpha-amylase OS=Pyrococcus horikoshii (strain ATCC 700860 / DSM 12428 / JCM 9974 / NBRC 100139 / OT-3) OX=70601 GN=amyA PE=3 SV=1