The proteinaceous noncompetitive inhibitor of starch phosphorylase (SP) isolated from the root of sweet potato (Ipomoea batatas [L.]Lam.) has been identified as a β-amylase (BA). For clar-ifying ambiguities about the physiological roles played by SP and BA, it seems essential to elucidate the molecular mechanism of SP inhibition against BA. A part of enzyme kinetics experiment supported the mechanism of endproduct inhibition of SP or BA, or the depletion of starch by the amylolytic action of BA. On the contrary, the hypothesis of BA directly bindjng or interacting with SP was also supported by BA acting as a proteinaceous noncompetitive inhibitor. Therefore, the above three possible molecular mechanisms need to be investigated deeply. We also inspected some other possible mechanisms. 由甘藷(Ipomoea batatas [L.] Lam.)中分離出來，對澱粉磷解酶(SP)具非競爭性抑制作用的蛋白質，經鑑定已知為β-澱粉水解酶(BA)。為了釐清澱粉磷解酶與β-澱粉水解酶所扮演的生理模糊角色，必須闡明β-澱粉水解酶抑制澱粉磷解酶的分子機轉。部分酵素動力學實驗的結果，支持兩者酵素於反應後，終產物抑制的理論及β-水解酶競爭共同受質(澱粉)，導致受質不足理論。相反的，β-澱粉水解酶對澱粉磷解酶之非競爭性抑制作用，也能解釋為酵素相互結合理論。因此，上述三種可能機制要更深入研究，並應觀測其他可能之機制。
