Table 1. The number of unique p-sites and phosphoproteins identified in the various phosphorylation compendiums and subsets.

	Total p-Sites	Total p-Sites Found in PFAM Domains	Highly Confident p-Sites	Highly Confident p-Sites Found in PFAM Domains	Phosphoproteins	Phosphoproteins with Highly Confident p-Sites
12UHQ	9783	2059	2566 (26%)	431	2374	1112 (47%)
20UHQ (only HTP)	13,244	2625	4156 (31%)	698	2587	1421 (55%)
21UHQ (including PG2)	14,339	3036	5519 (38%)	1175	2633	1557 (59%)
21UHQ metabolism (including PG2)	1668	527	499	99	412	197
21UHQ metabolism essential proteins (including PG2)	339	153	79	34	71	36

p-sites identified in three or more experiments are designated as Highly Confident. 12UHQ refers to the Amoutzias et al. (2012) dataset. 20UHQ (only HTP) refers to the p-sites identified by 20 HTP experiments in Vlastaridis et al. (2017). 21UHQ (including PG2) refers to the p-sites identified by 20 HTP experiments and by PhosphoGrid2 in Vlastaridis et al. (2017). 21UHQ metabolism (including PG2) refers to the p-sites identified by 20 HTP experiments and by PhosphoGrid2 in Vlastaridis et al. (2017) that were in metabolic proteins. 21UHQ metabolism essential proteins (including PG2) refers to p-sites identified by 20 HTP experiments and by PhosphoGrid2 in Vlastaridis et al. (2017) that were in essential metabolic proteins. p-site, phosphorylation site; HTP, high-throughput.