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 phosphorylation is targeted to Ser6 within a sequence Arg/Lys/Lys-Phe-Ser, which is conserved in all sucrase-isomaltase sequences known so far. By dephosphorylation of native sucrase-isomaltase with an immobilized acid phosphatase and rephosphorylation with protein kinase A, it is shown that Ser6 may be partially phosphorylated in vivo, raising the possibility that the tail itself and its phosphorylation by protein kinase A may be physiologically significant.