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Gingipain
Gingipains are trypsin-like cysteine proteinases produced by Porphyromonas gingivalis, a major cause of chronic periodontitis, serving as its principal virulence factors and drug targets linked to Alzheimer's and Parkinson's disease.
Glucan biosynthesis protein C
Glucan biosynthesis protein C (MdoC/OpgC, gene opgC, b1047) is the membrane-bound succinyltransferase of E. coli that succinylates osmoregulated periplasmic glucans, giving them their anionic character.
Glucoamylase
Glucoamylase (amyloglucosidase, γ-amylase, EC 3.2.1.3) is an exo-acting GH15 inverting enzyme releasing β-glucose from starch α-1,4 and α-1,6 bonds, used industrially for saccharification to glucose syrups and ethanol.
Glucosamine-6-phosphate isomerase
Glucosamine-6-phosphate isomerase, also called glucosamine-6-phosphate deaminase or NagB, is a bacterial enzyme that converts D-glucosamine-6-phosphate into fructose-6-phosphate, releasing ammonia and linking amino sugar metabolism to glycolysis.
Glucose-1-phosphate thymidylyltransferase, short form
Glucose-1-phosphate thymidylyltransferase, short form (IPR005907, RmlA/RfbA/RffH) is a bacterial homotetrameric EC 2.7.7.24 enzyme, first of four steps in dTDP-L-rhamnose cell wall biosynthesis, feedback-inhibited by dTDP-L-rhamnose and absent from humans.
Glucose-6-phosphatase
Glucose-6-phosphatase (G6Pase, EC 3.1.3.9; subunits G6PC1, G6PC2, G6PC3) is an ER enzyme complex hydrolyzing glucose-6-phosphate to glucose and phosphate, the final step of glycogenolysis and gluconeogenesis; defects cause glycogen storage disease type I.
Glucosyltransferase
Glucosyltransferase: glucose-transferring glycosyltransferase (EC 2.4.1.5) building glucans from donors like UDP-glucose and sucrose; a B. subtilis/S. salivarius version is FDA GRAS (GRN 1210, 2025).
Glucuronic acid
Glucuronic acid: C6-oxidized glucose sugar acid; as UDP-glucuronic acid it drives hepatic glucuronidation of bilirubin, hormones, and drugs via UGT enzymes (40-75% of xenobiotic elimination), and gut microbial beta-glucuronidases reverse the conjugation.
Glucuronidation
Glucuronidation: phase II metabolism in which UGT enzymes attach glucuronic acid from UDP-glucuronic acid to drugs and endobiotics like bilirubin, forming water-soluble glucuronides excreted via transporters; UGT1A1, UGT2B7, inhibition, induction, polymorphisms.
Glucuronoxylan synthase
Glucuronoxylan synthase is the Golgi-localized glycosyltransferase complex, built from IRX9, IRX10, and IRX14 proteins, that synthesizes the xylan backbone of glucuronoxylan in plant cell walls.
Glutamate racemase
Glutamate racemase (MurI, RacE, EC 5.1.1.3) is a cofactor-independent bacterial enzyme converting L-glutamate to D-glutamate for peptidoglycan cell wall synthesis, using two conserved cysteines; essential and an antibacterial drug target.
Glutamate--cysteine ligase
Glutamate--cysteine ligase (GCL, EC 6.3.2.2; formerly γ-glutamylcysteine synthetase) is the ATP- and magnesium-dependent heterodimeric enzyme (GCLC + GCLM subunits) catalyzing the rate-limiting first step of glutathione synthesis, forming γ-glutamylcysteine from glutamate and cysteine.
Glutaminase
Glutaminase (GLS/GLS2; EC 3.5.1.2) is a mitochondrial enzyme hydrolyzing glutamine to glutamate and ammonium, central to renal ammoniagenesis, hepatic ureagenesis, and glutamine-addicted cancer; its inhibitor telaglenastat (CB-839) reached phase II trials.
Glutamine amidotransferase
Glutamine amidotransferases (GATs, GATase domains) are two-domain enzymes that hydrolyze glutamine to glutamate and channel ammonia 10–40 Å to a synthase domain, supplying nitrogen for nucleotides, amino acids, amino sugars, coenzymes, and antibiotics; class I uses a Cys-His-Glu triad, class II an N-terminal cysteine of the Ntn-hydrolase fold.
Glutamine Synthetase
Glutamine synthetase (EC 6.3.1.2, L-glutamate:ammonia ligase) is the ATP-dependent enzyme assimilating ammonium into glutamine; types GSI, GSII, GSIII predate LUCA and it anchors nitrogen metabolism in bacteria, plants, and brain.
Glutamyl-tRNA reductase
Glutamyl-tRNA reductase (GluTR) is an NADPH-dependent oxidoreductase that reduces tRNA-bound glutamate to glutamate-1-semialdehyde, the first committed and rate-limiting step of tetrapyrrole biosynthesis in plants, algae, and some bacteria.
Glutaryl-CoA dehydrogenase
Glutaryl-CoA dehydrogenase (GCDH, EC 1.3.8.6) is a mitochondrial FAD-dependent homotetrameric enzyme catalyzing glutaryl-CoA to crotonyl-CoA in lysine and tryptophan breakdown; deficiency causes glutaric aciduria type 1.
Glutathione peroxidase
Glutathione peroxidase (GPx, EC 1.11.1.9), a selenium-containing antioxidant enzyme family (GPx1–GPx8) discovered in 1957, reduces hydrogen peroxide and lipid hydroperoxides using glutathione; GPx1 was the first mammalian selenoprotein.
Glutathione synthase
Glutathione synthase (glutathione synthetase, GSS, EC 6.3.2.3) is the homodimeric ATP-grasp enzyme catalyzing the second, ATP-dependent step of glutathione synthesis, adding glycine to γ-glutamylcysteine; GSS mutations cause rare autosomal recessive glutathione synthetase deficiency.
Glyceraldehyde-3-phosphate dehydrogenase 3
Glyceraldehyde-3-phosphate dehydrogenase 3 (GAPDH 3, TDH3/GPD3/YGR192C) is one of three 332-amino-acid Saccharomyces cerevisiae GAPDH isoenzymes catalyzing G3P to 1,3-bisphosphoglycerate with NAD+ in glycolysis.
Glycerate kinase
Glycerate kinase (EC 2.7.1.31, GLYK/GLYCTK) is a kinase phosphorylating D-glycerate with ATP to 3-phosphoglycerate in plants (photorespiration) or 2-phosphoglycerate in bacteria and animals; three unrelated protein classes exist.
Glycerol dehydrogenase
Glycerol dehydrogenase (EC 1.1.1.6, GldA/DhaD) is a zinc-dependent, NAD+-dependent oxidoreductase converting glycerol to dihydroxyacetone; distinct from glycerol dehydratase, it initiates oxidative glycerol metabolism and serves DHA production, cofactor regeneration, and triglyceride assays.
Glycerophospholipid cholesterol acyltransferase
Glycerophospholipid cholesterol acyltransferase (GCAT, EC 2.3.1.43) is a bacterial Aeromonas enzyme, an LCAT analogue, that transfers acyl groups from phospholipids to cholesterol; a Bacillus licheniformis-produced variant is a GRAS food processing aid (GRN 265, FoodPro LysoMaxa Oil) used for emulsification in egg yolk, meat, dairy, and oil degumming.
Glycine reductase complex selenoprotein A
Glycine reductase complex selenoprotein A (glycine reductase A, GRDA) is the selenocysteine-containing component A of the clostridial glycine reductase complex from Clostridium sticklandii, the first protein shown to contain selenium as selenocysteine, encoded by UGA.
Glycoamylase-like, conserved domain
Glycoamylase-like conserved domain: the GH15 glucoamylase catalytic domain, an inverting (α/α)6-barrel exo-hydrolase (EC 3.2.1.3) releasing β-glucose from starch, with Glu acid/base catalysis and an O-glycosylated linker to a starch-binding domain.
Glycogen debranching enzyme
Glycogen debranching enzyme (GDE, AGL gene product; amylo-1,6-glucosidase, 4-α-glucanotransferase) is a bifunctional enzyme that removes glycogen branch points during glycogenolysis; its deficiency causes glycogen storage disease type III (Cori/Forbes disease).
Glycogen synthase
Glycogen synthase (EC 2.4.1.11, GYS1/GYS2) is the rate-limiting UDP-glucose-dependent enzyme elongating glycogen's alpha-1,4 chains, regulated by phosphorylation and glucose-6-phosphate; GYS2 deficiency causes GSD type 0a.
Glycogen Synthase Kinase-3
Glycogen synthase kinase-3 (GSK-3, GSK3), serine/threonine kinase with paralogs GSK3α and GSK3β; phosphorylates primed substrates, regulates insulin and Wnt/β-catenin signaling; drug target for diabetes, Alzheimer's, and cancer.
Glycogenin
Glycogenin (GYG1/GYG2): self-glucosylating glucosyltransferase priming glycogen synthesis by attaching glucose to Tyr194/195 via a glucose-tyrosine bond; later found dispensable in knockout mice.
Glycogenin-1
Glycogenin-1 (GYG1, 3q24) is the self-glucosylating primer enzyme of glycogen synthesis in human muscle and heart; biallelic GYG1 mutations cause glycogen storage disease XV with polyglucosan storage, and glycogen can form without it.