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. 2000 Oct 20;1498(1):64-71.
doi: 10.1016/s0167-4889(00)00077-x.

Subcellular localization of cyclic ADP-ribosyl cyclase and cyclic ADP-ribose hydrolase activities in porcine airway smooth muscle

T A White  1 , S Johnson, T F Walseth, H C Lee, R M Graeff, C B Munshi, Y S Prakash, G C Sieck, M S Kannan
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Free article

Subcellular localization of cyclic ADP-ribosyl cyclase and cyclic ADP-ribose hydrolase activities in porcine airway smooth muscle

T A White et al. Biochim Biophys Acta. .
Free article

Abstract

Recent studies have provided evidence for a role of cyclic ADP-ribose (cADPR) in the regulation of intracellular calcium in smooth muscles of the intestine, blood vessels and airways. We investigated the presence and subcellular localization of ADP-ribosyl cyclase, the enzyme that catalyzes the conversion of beta-NAD(+) to cADPR, and cADPR hydrolase, the enzyme that degrades cADPR to ADPR, in tracheal smooth muscle (TSM). Sucrose density fractionation of TSM crude membranes provided evidence that ADP-ribosyl cyclase and cADPR hydrolase activities were associated with a fraction enriched in 5'-nucleotidase activity, a plasma membrane marker enzyme, but not in a fraction enriched in either sarcoplasmic endoplasmic reticulum calcium ATPase or ryanodine receptor channels, both sarcoplasmic reticulum markers. The ADP-ribosyl cyclase and cADPR hydrolase activities comigrated at a molecular weight of approximately 40 kDa on SDS-PAGE. This comigration was confirmed by gel filtration chromatography. Investigation of kinetics yielded K(m) values of 30.4+/-1.5 and 695. 3+/-171.2 microM and V(max) values of 330.4+/-90 and 102.8+/-17.1 nmol/mg/h for ADP-ribosyl cyclase and cADPR hydrolase, respectively. These results suggest a possible role for cADPR as an endogenous modulator of [Ca(2+)](i) in porcine TSM cells.

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