Table 1.

KEGG identifiers

Category	Database	Object	DB	Entry prefix	Example
Systems information	PATHWAY	KEGG pathway map	path	map, ko, ec, rn, <org>	map00300 (Lysine biosynthesis pathway) hsa04010 (Human MAPK signaling pathway)
	BRITE	BRITE hierarchy or table (classification system)	br	br, jp, ko, <org>	ko02000 (Transporter classification)
	MODULE	KEGG module	md	M, <org>_M	M00433 (Lysine biosynthesis module)
Genomic information	KO	Functional ortholog	ko	K	K01655 (Homocitrate synthase)
	GENOME	KEGG organism (complete genome)	gn	T	T01001 (Homo sapiens) gn:hsa (Homo sapiens)
	GENES	Gene and protein	<org>	–	hsa:1956 (EGFR)
Chemical information	COMPOUND	Small molecule	cpd	C	C01290 (Lactosylceramide)
	GLYCAN	Glycan	gl	G	G00092 (Lactosylceramide)
	REACTION	Biochemical reaction	rn	R	R03355
	RCLASS	Reaction class	rc	RC	RC00049
	ENZYME	Enzyme nomenclature	ec	–	ec:3.2.1.23 (beta‐Galactosidase)
Health information	NETWORK	Network variation map Network element	ne	nt N	nt06210 (ERK signaling) N00014 (Mutation‐activated EGFR signaling)
	VARIANT	Human gene variant	hsa_var	–	hsa_var:1956v2 (EGFR mutation)
	DISEASE	Human disease	ds	H	H00014 (Non‐small cell lung cancer)
	DRUG	Drug	dr	D	D01977 (Gefitinib)
	DGROUP	Drug group	dg	DG	DG01917 (Receptor tyrosine kinase inhibitor)
	ENVIRON	Health‐related substance	ev	E	E00017 (Opium)

<org>: organism code such as hsa for Homo sapiens.