| Hyaluronic acid | Humans and other mammals | Not Available | 2 | Details |
| Hyaluronidase enzymes | Humans | This represents a group of enzymes in humans responsible for the metabolism of hyaluronic acid. | 6 | Details |
| Hydrogen ions | Not Available | Not Available | 4 | Details |
| Hydrogen potassium ATPase | Humans | Gastric hydrogen potassium ATPase, also known as H+/K+ ATPase, is an enzyme which functions to acidify the stomach. | 6 | Details |
| Hydrolase | Alicyclobacillus acidocaldarius | Not Available | 1 | Details |
| Hydroxyacid oxidase 1 mRNA | Humans | Not Available | 1 | Details |
| Hydroxyacid-oxoacid transhydrogenase, mitochondrial | Humans | Catalyzes the cofactor-independent reversible oxidation of gamma-hydroxybutyrate (GHB) to succinic semialdehyde (SSA)... more | 1 | Details |
| Hydroxyacyl-coenzyme A dehydrogenase, mitochondrial | Humans | Mitochondrial fatty acid beta-oxidation enzyme that catalyzes the third step of the beta-oxidation cycle for medium a... more | 4 | Details |
| Hydroxyacylglutathione hydrolase, mitochondrial | Humans | Thiolesterase that catalyzes the hydrolysis of S-D-lactoyl-glutathione to form glutathione and D-lactic acid | 2 | Details |
| Hydroxyapatite | Humans | Not Available | 11 | Details |
| Hydroxycarboxylic acid receptor 2 | Humans | Acts as a high affinity receptor for both nicotinic acid (also known as niacin) and (D)-beta-hydroxybutyrate and medi... more | 10 | Details |
| Hydroxycarboxylic acid receptor 3 | Humans | G protein-coupled receptor for 3-hydroxyoctanoate, a fatty acid beta-oxidation intermediate. Signals through the inhi... more | 3 | Details |
| Hydroxyethylthiazole kinase | Bacillus subtilis (strain 168) | Catalyzes the phosphorylation of the hydroxyl group of 4-methyl-5-beta-hydroxyethylthiazole (THZ). | 1 | Details |
| Hydroxylamine reductase | Desulfovibrio vulgaris (strain Hildenborough / ATCC 29579 / NCIMB 8303) | Catalyzes the reduction of hydroxylamine to form NH(3) and H(2)O. | 1 | Details |
| Hydroxylamine reductase | Desulfovibrio desulfuricans (strain ATCC 27774 / DSM 6949) | Catalyzes the reduction of hydroxylamine to form NH(3) and H(2)O. | 2 | Details |
| Hydroxylapatite | Humans | Not Available | 8 | Details |
| Hydroxymethylglutaryl-CoA lyase, mitochondrial | Humans | Mitochondrial 3-hydroxy-3-methylglutaryl-CoA lyase that catalyzes a cation-dependent cleavage of (S)-3-hydroxy-3-meth... more | 1 | Details |
| Hydroxymethylglutaryl-CoA synthase, cytoplasmic | Humans | Catalyzes the condensation of acetyl-CoA with acetoacetyl-CoA to form HMG-CoA, which is converted by HMG-CoA reductas... more | 1 | Details |
| Hydroxymethylpyrimidine/phosphomethylpyrimidine kinase | Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720) | Catalyzes the phosphorylation of hydroxymethylpyrimidine phosphate (HMP-P) to HMP-PP, and of HMP to HMP-P. | 1 | Details |
| Hydroxymycolate synthase MmaA4 | Mycobacterium tuberculosis | Involved in the biosynthesis of hydroxymycolate, a common precursor of oxygenated mycolic acids (methoxy-mycolate and... more | 1 | Details |
| Hydroxyproline dehydrogenase | Humans | Dehydrogenase that converts trans-4-L-hydroxyproline to delta-1-pyrroline-3-hydroxy-5-carboxylate (Hyp) using ubiquin... more | 1 | Details |
| Hydroxyquinol 1,2-dioxygenase | Nocardioides simplex | Catalyzes the ortho-cleavage of the aromatic ring of hydroxyquinol. | 1 | Details |
| Hypocretin neuropeptide precursor | Humans | Neuropeptides that play a significant role in the regulation of food intake and sleep-wakefulness, possibly by coordi... more | 1 | Details |
| Hypothetical conserved protein | Thermus thermophilus (strain HB27 / ATCC BAA-163 / DSM 7039) | Not Available | 1 | Details |
| Hypothetical cytosolic protein | Syntrophus aciditrophicus (strain SB) | Not Available | 1 | Details |