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CHARACTERIZATION OF AN α‐AMIDATING ACTIVITY IN A HUMAN PANCREATIC TUMOUR SECRETING VASOACTIVE INTESTINAL PEPTIDE (VIP)
Author(s) -
MALTÉSE J.Y.,
MONGE G.,
GIRAUD P.,
SALERS P.,
OUAFIK LH.,
PELEN F.,
OLIVER C.
Publication year - 1990
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.1990.tb03884.x
Subject(s) - vasoactive intestinal peptide , endocrinology , enzyme , medicine , achlorhydria , pancreas , chemistry , biological activity , enzyme assay , biochemistry , biology , neuropeptide , in vitro , receptor , stomach
SUMMARY A case of watery diarrhoea hypokalemia achlorhydria (WDHA) syndrome due to a pancreatic tumour and identified by VIP plasma level, VIP immunocyto‐chemistry, and ultrastructural analysis of tumour sections, is reported, Since VIP is the mediator of the syndrome and is biologically active under its amidated form, the enzymatic α‐amidating activity was investigated and characterized in tumour extract; using the synthetic substrate D‐Tyr‐Val‐Gly, the enzyme displayed an optimal activity at pH 70, under aerobic conditions and with 35 μM CuSO4 and 3 mM ascorbate as co‐factors. The K max and V max values of the enzymatic activity were 133.7 μM and 26.9 pmol/h/μg protein respectively. Its molecular weight, determined by molecular sieving, was close to 36 kDa. Other tumours of the human endocrine pancreas were also investigated for the enzymatic activity. The clinical interest of studying the regulation of the α‐amidating activity in such tumours is discussed.