PMID-sentid Pub_year Sent_text comp_official_name comp_offsetprotein_name organism prot_offset 12559972-2 2003 Since transphosphorylation of the two kinases is presumed to occur after receptor engagement we examined the phosphorylation by recombinant JAK3 of a peptide substrate corresponding to the JAK1 activation loop (KAIETDKEYYTVKD), which has two adjacent tyrosines. Tyrosine 251-260 Janus kinase 1 Homo sapiens 189-193 12559972-5 2003 Kinetic analysis of the reactions of singly phosphorylated JAK1 activation loop peptides showed that phosphorylating the first or second tyrosine decreased the k(cat)/K(m) for the phosphorylation of the other 115- and 26-fold, respectively. Tyrosine 137-145 Janus kinase 1 Homo sapiens 59-63