Cholecystokinin purification

Natural somatostatin is a cyclic decatetrapeptide (SS-14) originally discovered from rat hypothalamus during the purification of growth hormone-releasing factor and subsequently isolated from sheep and pig hypothalamus [32-34]. Synthetic SS-14 (Table 1) has been found to show antisecretory effects on various body tissues including pituitary, pancreatic a and p cells as well as decrease of serotonin and cholecystokinin secretion. 

Before the advent of high-speed CCC, the method was utilized for the purification of various samples such as synthetic peptides, cholecystokinin analogs, and then-fragments (HCPC Table 1). 

This material has been purified further to an activity of about 3, 000 Ivy dog units of cholecystokinin per mg by filtration through a Sephadex G-50 column at pH 8. 0 followed by chromatography on Amberlite XE-64 at pH 7. 5 (Jorpes, Mutt, Toczko 1964), During these last purification steps the secretin is completely removed, but the cholecystokinin and pancreozymin activities once again go parallel. 

Pancreozymin. As pointed out by the present authors in 1961 and 1962, it is quite remarkable how closely cholecystokinin and pancreozymin accompany each other during the various purification steps, whereas secretin separates very early. This applies to the chromatography on the acidic carboxymethyl cellulose and on the basic TEAE-cellulose up to a strength of 200-250 Ivy dog units of CCK per mg substance. 

---