Isolation and characterization of sulphated and nonsulphated forms of cholecystokinin-58 and their action on gallbladder contraction

Cholecystokinin (CCK) exists in multiple molecular forms with different pol ypeptide lengths and the absence or presence of sulphation. We have isolate d sulphated and nonsulphated forms of CCK-58 from porcine intestine and hav e determined their bioactivities in a guinea-pig gallbladder contraction as say. Both farms co-eluted in cation-exchange chromatography and in several rounds of reverse-phase (RP)-HPLC, but separated upon RP-HPLC using a water /acetonitrile system with heptafluorobutyric acid as counter ion. Nonsulpha ted CCK-58 was the form detected by matrix-assisted laser desorption/ioniza tion (MALDI) mass spectrometry because of desulphation in that process. The biological activity of CCK-58 and CCK-33 is equipotent, although the kinet ics of the response differ. Sulphated CCK-58 was found to be 35 times mon p otent than nonsulphated CCK-58. In contrast, sulphated CCK-8 is 150 times m ore potent than nonsulphated CCK-8, and for sulphated and nonsulphated CCK- 33, the activities differ by a factor of 100. This type of correlation indi cates that the N-terminal end of CCK-58 partially compensates for the decre ase in activity arising from the lack of sulphated tyrosine. Given its fair ly high bioactivity, nonsulphated CCK-58 may have a physiological significa nce.