passages.id: split_8_test_15_passage
passages.type: progene_text
passages.text: The inhibition by the RIalpha subunit is reversed by addition of nanomolar concentrations of cAMP ( Ka = 40 nM ) , thus demonstrating that PrKX is a novel , type I cAMP - dependent protein kinase that is activated at lower cAMP concentrations than the holoenzyme with the Calpha subunit of cAMP - dependent protein kinase .