Kinase annotations question

[ravitharakan]

Hi Hani and team, thank you for making such a useful package! I have a question about the PhosphoSitePlus annotations. It seems for many kinases, there are only a few annotated phosphosites. For example for mouse JAK1, a kinase we are interested in, the annotation is only

PhosphoSite.mouse$JAK1
[1] "STAT3;Y705;" "PTPN11;Y327;" "PTPN11;Y304;" "IL7R;Y449;"

JAK1 is known to phosphorylate STAT1 and STAT2, so it is surprising those annotations are not there. How are the annotations derived from PhosphoSitePlus? Can they be extended?