Some aspects of the roles of inositol trisphosphate (Insp3) and inosit
ol tetrakisphosphate (Insp4) in Ca2+ homeostasis in terms of inositol
trisphosphate 3-kinase B (IP3K-B) localization and activity are discus
sed. The model that rye propose is also compatible with IP3K-B partici
pating in the widely reported phenomenon of quantal release of Ca2+ fr
om internal stores, at least in some biological systems. (C) 1997 Fede
ration of European Biochemical Societies.