DEMONSTRATION OF THE PRESENCE OF CYCLIC INOSITOL PHOSPHOHYDROLASE IN HUMAN URINE

Cyclic inositol phosphohydrolase (cIPH), cleaves the cyclic bond of cy clic inositol monophosphate (cIP) to yield inositol monophosphate. In this communication, we demonstrate the presence of cIPH in human urine . cIPH was measured in the 24-h urine samples of both male and female hospital patients. cIPH released per day ranged from 0 to 243 units in men (n = 16) and from 15 to 346 units in women (n = 18). Release of c IPH activity was not related to renal function as measured by creatini ne clearance. HPLC ion-exchange chromatography or HPLC gel filtration of ammonium sulfate precipitate yielded a distinct cIPH peak with an a pparent molecular weight of 40 kDa on gel filtration. This is the firs t demonstration of the presence of this enzyme in human urine. The lar ge variation (over 20-fold) in the excretion of this protein suggests that it may have physiological and/or pathological significance. (C) 1 997 Academic Press.