. Author manuscript; available in PMC: 2025 Mar 1.

Published in final edited form as: Mass Spectrom Rev. 2022 Sep 27;43(2):289–326. doi: 10.1002/mas.21811

TABLE 1.

Summary of the number of reviewed proteins listed in the UniprotKB database searched by a unique keyword (KW)^a

Code	Keyword	# Reviewed proteins	# Human proteins

KW-9991	All PTMs	122,905	13,951
KW-0597	Phosphoprotein	48,652	8245
KW-0325	Glycoprotein	32,275	4686
KW-0007	Acetylation	18,417	3419
KW-0832	Ubiquitinylation	10,675	2517
KW-0488	Methylation	8552	1001
KW-0013	ADP-ribosylation	568	105
KW-0765	Tyrosine sulfation	548	47
KW-0944	Tyrosine nitration	243	48

Note: Each PTM has a unique code assigned. Accessed on 9–1-2022.

More than one PTM can comodify a single protein.