木薯分支酶活性测定及同工酶电泳技术应用初探

Preliminary Study of SBE Activity and it's Isozyme Electrophoresis in Manihot esculenta Crantz

淀粉分支酶(Starch branching enzyme,SBE)是唯一引入α-1,6糖苷键分支点,催化支链淀粉形成的酶,影响淀粉分支程度及淀粉粒的精细结构。本文以3个亲缘关系较远的高产木薯品种(SC124、SC8、Arg7)为材料,利用SBE同工酶电泳及酶活性检测观察木薯块根支链淀粉增长较快时期SBE活性变化动态,结合支链淀粉含量检测分析木薯淀粉同工酶表达特点与支链淀粉积累的关系。结果表明:种植后140d至180d为木薯单株支链淀粉含量快速增加时期;SC124和SC8支链淀粉积累量早于Arg7达到高峰;Arg7各个时期的支链淀粉含量及SBE活性均表现最高。同工酶分析表明,木薯分支酶有SBE-I和SBE-II两个基因位点:SBE-Ι至少有3个等位基因位点(SBE-Ιa、SBE-Ιb、SBE-Ιc),品种间具有多态性;SBE-II为单一条带,但活性大小在品种间和发育不同阶段有差异。初步判定等位基因位点SBE-Ιc和SBE-II可能对SBE酶活性和支链淀粉含量贡献较大。

Starch branching enzyme（SBE） is a unique enzyme that introduces α-1,6 branching points in the amylopectin molecules,which is a key enzyme for embranchment and elaborate structure of amylopectin.In this research,three cassava cultivars（SC124,SC8,Arg7） with far relationship and highyielding were used for the analysis of SBE activity and it＇s isozyme electrophoresis.The correlation between isozyme loci,enzyme activities of SBE,and starch content were investigated.The results showed that the rapid accumulating stage of amylopectin content per plant was on 140～180 d after planting;the peak of amylopectin accumulation in SC124 and SC8 appeared much earlier than that in Arg7,but the amylopectin content and SBE activity of Arg7 was much higher than the other two cultivars.SBE-Ι manifested genetic diversity among three cultivars,while SBE-Ⅱ did not exhibit genetic polymorphism,but showed differentiation in activity among different varieties and developing stages.The loci of SBEΙc and SBEⅡmay provide much great contribution to SBE activity and amylopectin content.