【摘要】 大麦极限糊精酶(LD,EC 3.2.1.41)是麦芽中淀粉水解的重要酶类之一,主要负责催化支链淀粉和极限糊精内部的-α1,6-D糖苷键;自上世纪40年代极限糊精酶被发现以来,酶的提纯和活性测定方法不断得到改进.在籽粒发育过程中,自由态的酶活性先升后降,束缚态的酶出现较晚,其活性上升与自由态酶活性下降相衔接.成熟籽粒中酶活性很低,发芽过程中酶的总活性逐渐增强.近年来从一个噬菌体基因组的文库中分离得到了编码大麦极限糊精酶的基因,并发现在籽粒中存在着与极限糊精酶形成复合物的两类抑制因子,它们在制啤过程中有双重作用.本文对大麦极限糊精酶的活性变化及其影响因素、基因型差异、测定方法以及相关基因的分离等方面进行了综述.更多还原

【Abstract】 The starch debranching enzyme limit dextrinase(LD,EC 3.2.1.41) is one of the key enzymes in malting,which catalyses the hydrolysis of α-1,6-D-glucosidic bonds in amylopectin and limit dextrin.The methods for purification and activity measurement of the enzyme have been much improved since it was discovered in 1940’s.During grain development,the activity of free LD increased initially and then decreased,while the bound LD appeared later,and the increase in its activity is closely associated with the decrease in the activity of free LD.The activity of LD was quite low in mature grains.However,the total activity increased gradually during germination.Recently,the gene encoding barley LD was isolated from a genomic phage library using a barley cDNA clone as probe and the two inhibitors which could form complex with LD in grains also were identified and characterized.It is indicated that the inhibitors have dual impacts on malting process and quality.In this paper the change in LD activity during grain development and germination and its response to environmental factors,genotypic difference and methodology of assaying the activity,and isolation of the genes encoding the enzyme were reviewed.更多还原