cd00413, Glyco_hydrolase_16, glycosyl hydrolase family 16. The O-Glycosyl hydrolases are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A glycosyl hydrolase classification system based on sequence similarity has led to the definition of more than 95 different families inlcuding glycosyl hydrolase family 16. Family 16 includes lichenase, xyloglucan endotransglycosylase (XET), beta-agarase, kappa-carrageenase, endo-beta-1,3-glucanase, endo-beta-1,3-1,4-glucanase, and endo-beta-galactosidase, all of which have a conserved jelly roll fold with a deep active site channel harboring the catalytic residues.
cd05327, retinol-DH_like_SDR_c_like, retinol dehydrogenase (retinol-DH), Light dependent Protochlorophyllide (Pchlide) OxidoReductase (LPOR) and related proteins, classical (c) SDRs. Classical SDR subgroup containing retinol-DHs, LPORs, and related proteins. Retinol is processed by a medium chain alcohol dehydrogenase followed by retinol-DHs. Pchlide reductases act in chlorophyll biosynthesis. There are distinct enzymes that catalyze Pchlide reduction in light or dark conditions. Light-dependent reduction is via an NADP-dependent SDR, LPOR. Proteins in this subfamily share the glycine-rich NAD-binding motif of the classical SDRs, have a partial match to the canonical active site tetrad, but lack the typical active site Ser. This subgroup includes the human proteins: retinol dehydrogenase -12, -13 ,and -14, dehydrogenase/reductase SDR family member (DHRS)-12 , -13 and -X (a DHRS on chromosome X), and WWOX (WW domain-containing oxidoreductase), as well as a Neurospora crassa SDR encoded by the blue light inducible bli-4 gene. SDRs are a functionally diverse family of oxidoreductases that have a single domain with a structurally conserved Rossmann fold (alpha/beta folding pattern with a central beta-sheet), an NAD(P)(H)-binding region, and a structurally diverse C-terminal region. Classical SDRs are typically about 250 residues long, while extended SDRs are approximately 350 residues. Sequence identity between different SDR enzymes are typically in the 15-30% range, but the enzymes share the Rossmann fold NAD-binding motif and characteristic NAD-binding and catalytic sequence patterns. These enzymes catalyze a wide range of activities including the metabolism of steroids, cofactors, carbohydrates, lipids, aromatic compounds, and amino acids, and act in redox sensing. Classical SDRs have an TGXXX[AG]XG cofactor binding motif and a YXXXK active site motif, with the Tyr residue of the active site motif serving as a critical catalytic residue (Tyr-151, human 15-hydroxyprostaglandin dehydrogenase (15-PGDH) numbering). In addition to the Tyr and Lys, there is often an upstream Ser (Ser-138, 15-PGDH numbering) and/or an Asn (Asn-107, 15-PGDH numbering) contributing to the active site; while substrate binding is in the C-terminal region, which determines specificity. The standard reaction mechanism is a 4-pro-S hydride transfer and proton relay involving the conserved Tyr and Lys, a water molecule stabilized by Asn, and nicotinamide. Extended SDRs have additional elements in the C-terminal region, and typically have a TGXXGXXG cofactor binding motif. Complex (multidomain) SDRs such as ketoreductase domains of fatty acid synthase have a GGXGXXG NAD(P)-binding motif and an altered active site motif (YXXXN). Fungal type ketoacyl reductases have a TGXXXGX(1-2)G NAD(P)-binding motif. Some atypical SDRs have lost catalytic activity and/or have an unusual NAD(P)-binding motif and missing or unusual active site residues. Reactions catalyzed within the SDR family include isomerization, decarboxylation, epimerization, C=N bond reduction, dehydratase activity, dehalogenation, Enoyl-CoA reduction, and carbonyl-alcohol oxidoreduction.
cd06565, GH20_GcnA-like, Glycosyl hydrolase family 20 (GH20) catalytic domain of N-acetyl-beta-D-glucosaminidase (GcnA, also known as BhsA) and related proteins. GcnA is an exoglucosidase which cleaves N-acetyl-beta-D-galactosamine (NAG) and N-acetyl-beta-D-galactosamine residues from 4-methylumbelliferylated (4MU) substrates, as well as cleaving NAG from chito-oligosaccharides (i.e. NAG polymers). In contrast, sulfated forms of the substrate are unable to be cleaved and act instead as mild competitive inhibitors. Additionally, the enzyme is known to be poisoned by several first-row transition metals as well as by mercury. GcnA forms a homodimer with subunits comprised of three domains, an N-terminal zincin-like domain, this central catalytic GH20 domain, and a C-terminal alpha helical domain. The GH20 hexosaminidases are thought to act via a catalytic mechanism in which the catalytic nucleophile is not provided by solvent or the enzyme, but by the substrate itself.
cd13585, PBP2_TMBP_like, The periplasmic-binding component of ABC transport systems specific for trehalose/maltose and similar oligosaccharides; possess type 2 periplasmic binding fold. This family includes the periplasmic trehalose/maltose-binding component of an ABC transport system and related proteins from archaea and bacteria. Members of this group belong to the type 2 periplasmic-binding fold superfamily. PBP2 is comprised of two globular subdomains connected by a flexible hinge and bind their ligand in the cleft between these domains in a manner resembling a Venus flytrap. The majority of PBP2 proteins function in the uptake of small soluble substrates in eubacteria and archaea. After binding their specific ligand with high affinity, they can interact with a cognate membrane transport complex comprised of two integral membrane domains and two cytoplasmically located ATPase domains. This interaction triggers the ligand translocation across the cytoplasmic membrane energized by ATP hydrolysis.
TIGR00762, DegV, EDD domain protein, DegV family. This family of proteins is related to DegV of Bacillus subtilis and includes paralogous sets in several species (B. subtilis, Deinococcus radiodurans, Mycoplasma pneumoniae) that are closer in percent identity to each than to most homologs from other species. This suggests both recent paralogy and diversity of function. DegV itself is encoded immediately downstream of DegU, a transcriptional regulator of degradation, but is itself uncharacterized. Crystallography suggested a lipid-binding site, while comparison of the crystal structure to dihydroxyacetone kinase and to a mannose transporter EIIA domain suggests a conserved domain, EDD, with phosphotransferase activity. [Unknown function, General].
cd06423, CESA_like, CESA_like is the cellulose synthase superfamily. The cellulose synthase (CESA) superfamily includes a wide variety of glycosyltransferase family 2 enzymes that share the common characteristic of catalyzing the elongation of polysaccharide chains. The members include cellulose synthase catalytic subunit, chitin synthase, glucan biosynthesis protein and other families of CESA-like proteins. Cellulose synthase catalyzes the polymerization reaction of cellulose, an aggregate of unbranched polymers of beta-1,4-linked glucose residues in plants, most algae, some bacteria and fungi, and even some animals. In bacteria, algae and lower eukaryotes, there is a second unrelated type of cellulose synthase (Type II), which produces acylated cellulose, a derivative of cellulose. Chitin synthase catalyzes the incorporation of GlcNAc from substrate UDP-GlcNAc into chitin, which is a linear homopolymer of beta-(1,4)-linked GlcNAc residues and Glucan Biosynthesis protein catalyzes the elongation of beta-1,2 polyglucose chains of Glucan.
cd17325, MFS_MdtG_SLC18_like, bacterial MdtG-like and eukaryotic solute carrier 18 (SLC18) family of the Major Facilitator Superfamily of transporters. This family is composed of eukaryotic solute carrier 18 (SLC18) family transporters and related bacterial multidrug resistance (MDR) transporters including several proteins from Escherichia coli such as multidrug resistance protein MdtG, from Bacillus subtilis such as multidrug resistance proteins 1 (Bmr1) and 2 (Bmr2), and from Staphylococcus aureus such as quinolone resistance protein NorA. The family also includes Escherichia coli arabinose efflux transporters YfcJ and YhhS. MDR transporters are drug/H+ antiporters (DHA) that mediate the efflux of a variety of drugs and toxic compounds, and confer resistance to these compounds. The SLC18 transporter family includes vesicular monoamine transporters (VAT1 and VAT2), vesicular acetylcholine transporter (VAChT), and SLC18B1, which is proposed to be a vesicular polyamine transporter (VPAT). The MdtG/SLC18 family belongs to the Major Facilitator Superfamily (MFS) of membrane transport proteins, which are thought to function through a single substrate binding site, alternating-access mechanism involving a rocker-switch type of movement.
TIGR04285, parB-like_partition_protein, nucleoid occlusion protein. This model describes nucleoid occlusion protein, a close homolog to ParB chromosome partitioning proteins including Spo0J in Bacillus subtilis. Its gene often is located near the gene for the Spo0J ortholog. This protein bind a specific DNA sequence and blocks cytokinesis from happening until chromosome segregation is complete.
cd01277, HINT_subgroup, HINT (histidine triad nucleotide-binding protein) subgroup: Members of this CD belong to the superfamily of histidine triad hydrolases that act on alpha-phosphate of ribonucleotides. This subgroup includes members from all three forms of cellular life. Although the biochemical function has not been characterised for many of the members of this subgroup, the proteins from Yeast have been shown to be involved in secretion, peroxisome formation and gene expression.
TIGR04018, thioredoxin_reductase, putative bacillithiol system oxidoreductase, YpdA family. Members of this protein family, including YpdA from Bacillus subtilis, are apparent oxidoreductases present only in species with an active bacillithiol system. They have been suggested actually to be thiol disulfide oxidoreductases (TDOR), although the evidence is incomplete. [Unknown function, Enzymes of unknown specificity].
pfam12625, Arabinose_bd, Arabinose-binding domain of AraC transcription regulator, N-term. AraC is a bacterial transcriptional regulatory protein with a DNA-binding domain at the C-terminus, HTH_AraC, pfam00165, and this dimerization domain which harbours the arabinose-binding pocket at the N-terminus. AraC positively and negatively regulates expression of the proteins required for the uptake and catabolism of the sugar L-arabinose 1,2,3].
pfam00743, FMO-like, Flavin-binding monooxygenase-like. This family includes FMO proteins, cyclohexanone mono-oxygenase and a number of different mono-oxygenases.
