Preprocholecystokinin processing in the normal human anterior pituitary.
The processing of preprocholecystokinin in human pituitary extracts was investigated using gel and ion-exchange chromatography monitored by sequence-specific radioimmunoassays before and after incubation with trypsin, carboxypeptidase B, and arylsulfatase. Whereas the neural lobe contained only the bioactive alpha-carboxyamidated cholecystokinin (CCK) peptides (32 pmol/g), of which CCK-8 predominated, the anterior lobe contained substantial amounts of three large nonamidated procholecystokinin fragments (95 pmol/g; Mrs, 9000, 7000, and 5000) and small amounts of alpha-amidated CCK (8.3 pmol/g). The latter occurred only in the following large molecular forms: component I, CCK-58, and traces of CCK-33. Corticotrophic tumors processed the large forms to small CCK-8-like forms as are found in the brain and in the gut. The results show that a hormone gene, although translated, is expressed only to a limited extent as mature, active peptide outside the principal production region(s). Thus the processing of CCK to small alpha-amidated peptides in the less-differentiated tumor tissue supports the hypothesis that differentiation of endocrine cells may be sustained also at the posttranslational level.
Rehfeld
J F
JF
D000595:Amino Acid Sequence; D002766:Cholecystokinin / Q000032:analysis / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D007106:Immune Sera; D010446:Peptide Fragments / Q000032:analysis; D010903:Pituitary Gland, Anterior / Q000378:metabolism*; D010911:Pituitary Neoplasms / Q000032:analysis; D011498:Protein Precursors / Q000235:genetics / Q000302:isolation & purification*; D011499:Protein Processing, Post-Translational; D011863:Radioimmunoassay
D007106:Immune Sera; D010446:Peptide Fragments; D011498:Protein Precursors; C042082:preprocholecystokinin; D002766:Cholecystokinin