PHOSPHORYLATION OF THE N-TERMINAL INTRACELLULAR TAIL OF SUCRASE-ISOMALTASE BY CAMP-DEPENDENT PROTEIN-KINASE

This paper reports the phosphorylation of the intracellular N-terminal tail of sucrase-isomaltase by protein kinase A and shows that this ph osphorylation is targeted to Ser6 within a sequence Arg/Lys/Lys-Phe-Se r, which is conserved in all sucrase-isomaltase sequences known so far . By dephosphorylation of native sucrase-isomaltase with an immobilize d acid phosphatase and rephosphorylation with protein kinase A, it is shown that Ser6 may be partially phosphorylated in vivo, raising the p ossibility that the tail itself and its phosphorylation by protein kin ase A may be physiologically significant.