- Abhydrolase domain containing (ABHD)
- Acidic nuclear phosphoproteins (ANP32)
- Actin related protein 2/3 complex subunits (ARPC)
- Acyl-CoA synthetases (ACS)
- Acyl-CoA thioesterases (ACOT)
- ADAM metallopeptidase domain containing (ADAM)
- Table of ADAMs University of Virginia School of Medicine HGNC approved
- ADAM metallopeptidases with thrombospondin type 1 motif (ADAMTS)
- Adenylate kinases (AK)
- ADP-ribosylation factors (ARF)
- ADP-ribosylation factors-like (ARL)
- Adrenergic receptors (ADR)
- ADP-ribosylation factor GTPase activating proteins (ARFGAP)

- A-kinase anchor proteins (AKAP)
- Alcohol dehydrogenases (ADH)
- Aldehyde dehydrogenases (ALDH)
- Aldo-keto reductases (AKR)
- Alkylation repair homologs (ALKB)
- Amiloride-sensitive cation channels (ACCN)
- Aminoacyl tRNA synthetases
- Anaphase promoting complex subunits (ANAPC)
- Anoctamins (ANO)
- Annexins (ANXA)
- Apolipoprotein B mRNA editing enzymes (APOBEC)
- Aquaporins (AQP)

- Arachidonate lipoxygenases (ALOX)

- ATPases (ATP)
- ATP-binding cassette transporters (ABC)
- Baculoviral IAP repeat containing (BIRC)
- Basic helix-loop-helix (BHLH)
- BEN domain containing (BEN)
- Beta-galactoside-binding lectins (LGALS)
- Blood group antigens
- BPI fold containing (BPIF)

- Cadherins (CDH)
- S100 calcium binding proteins (S100)
- Calcium channels (CACN)

- Carbonic anhydrases (CA)

- Carboxylesterases (CES)
- Caspases (CASP)

- Cas scaffolding proteins (CASS)
- Cathepsins (CTS)
- CAZy Carbohydrate-Active enZYmes Database
- CD molecules (CD)
- HCDM Human Cell Differentiation Molecules oganisation (HLA8 to HCDM)
- CDC-like kinases (CLK)

- CDGSH iron sulfur domain containing (CISD)
- Charged multivesicular body proteins (CHMP)
- Chemokine ligands (CCL)

- Chemokine (C-C motif) receptors (CCR)

- Chemokine (C-X-C motif) receptors (CXCR)
- Chloride intracellular channels (CLIC)

- Cholinergic receptors (CHR)
- Chromatin-modifying enzymes
- Claudins (CLDN)

- Coiled-coil-helix-coiled-coil-helix domain containing (CHCHD)
- Collectins (COLEC)

- Complement system

- Components of oligomeric golgi complex (COG)
- C-type lectin domain containing (CLEC)
- Coronins (CORO)
- Cyclin-dependent kinases (CDK)
- Cytochrome b (CYB)

- Cytochrome P450s (CYP)
- Cytokines
- COPE Cytokines Online Pathfinder Encyclopaedia