“…Earlier studies have indicated that, e.g. in liver, NAD+ glycohydrolase is a constituent of endoplasmic reticulum, plasma membranes (Bock et al, 1971; Diaugustine et al, 1978), nuclear envelopes (Green & Dobrjansky, 1972;Fukushima et al, 1976;Tamulevicius et al, 1979) and secondary lysosomes (Mellors et al, 1975). The physiological role of this enzyme remains elusive; it was thought to control intracellular concentrations of NAD+ (Kaplan, 1966;Johnson, 1980), but its occurrence at high concentrations in certain tissues was difficult to reconcile with the known turnover rates of the coenzyme in vivo (Bock et al, 1968;Clark & Pinder, 1969;Bernofsky & Pankov, 1973).…”