Kinase, in vitro: 

An enzyme-substrate reaction that occurs in non-living experimental conditions such as a test tube. For example, a purified enzyme is reacted with a substrate protein or mixture of proteins or peptides.

p90RSK S44-p
 Putative in vivo kinases: 

An enzyme-substrate reaction that occurs within living cells; includes cultured cells, ex vivo samples, and intact organisms. In the case of kinases, the large number of protein kinases in intact cells makes exact identification of the responsible kinase challenging.

p90RSK S44-p
Regulatory protein:
PKCA S44-p
EGF S44-p
Go_6976 S44-p
okadaic_acid S44-p
phorbol_ester S44-p
SB203580 S44-p
serum S44-p
sorbitol S44-p
SP600125 S44-p
U0126 S44-p
UV S44-p