Abstract
Adenylate cyclase was assayed in a sonicated preparation of silkworm pupal fat body. The adenylate cyclase was found mostly in the particulate fraction. The activity depended upon either Mg2+ or Mn2+, and the degree of stimulation by Mn2+ was 2 times greater than that by Mg2+ compared at the saturating concentrations. In the presence of Mg2+, the enzyme was inhibited by both EGTA and high concentrations of Ca2+, showing biphasical response to Ca2+. The enzyme was stimulated several-fold by NaF. The enzyme exhibited typical Michaelis-Menten kinetics and Km values were 0.13 mM for MgATP and 0.086 mM for MnATP.

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