茶树中过氧化氢酶活力变化规律

Regulation of catalase activity variation of tea tree(Camellia sinensis)

用紫外分光光度法测定茶树鲜叶的过氧化氢酶(catalase,CAT)活力,研究茶树CAT活力变化规律.结果表明:相同地点种植的不同茶树品种在生长旺盛的春季,其新梢的酶活力虽然会有一定的差异,但总体上差异不明显,到了夏季各品种间的差异较大,秋季酶活力普遍较高,但差异减小;不同季节、同一品种的茶树CAT活力变化明显,总体表现为秋季>夏季>春季;生长在主干的鲜叶CAT活力高于新生枝条上的鲜叶,而在同一枝条上,位于枝条中间的鲜叶CAT活力高于位于枝条两端的鲜叶;刚采下来的茶树鲜叶在摊放2h后酶活力上升30%,而随着摊放时间的进一步延长,CAT活力持续下降,到12h后酶活力基本稳定在100U/g左右.可见,茶树CAT活力变化对茶树正常生长发育起着极为重要的作用,是茶树逆境生理的关键酶.

Summary Catalase （CAT） is a protective enzyme responsible for the degradation of hydrogen peroxide before it damages the cellular components . All aerobic organisms and many anaerobic organisms possess it in virtually . The catalatic reaction takes place in two steps ： The first hydrogen peroxide molecule oxidizes the heme to an oxyferryl species in which one oxidation equivalent is removed from the iron and one from the porphyrin ring to generate a porphyrin cation radical ; the second hydrogen peroxide is then used as a reductant of compound 1 to regenerate the resting state enzyme , water , and oxygen . But so far the reports about the CAT in tea tree （ Camellia sinensis ） are not seen so often . In this research , the regulation of CAT activity variation of tea tree was studied . The CAT was extracted from fresh tea leaves with 0 .2 mol/L phosphate buffer （ pH 7 .4） and 15% polyvinylpolypyrrolidone （ PVPP） . The CAT activity was measured spectrophotometrically at 240 nm . One unit of CAT activity was defined as the activity required to destroy 1 μmol H2 O2 at 25 ℃ in 0 .2 mol/L phosphate buffer for 1 min .The results about the regulations of tea CAT activity variation showed that , different cultivars of tea tree had different CAT activities , especially in summer . And the CAT activity varied when the season changed , and the activity variation tendency was as autumn ＆gt; summer ＆gt; spring . The leaves located in the older branch had a higher CAT activity than those in the new branch ; the leaves in vigorous grow th had a higher CAT activity than the new and old leaves . When spreading for 2 h , the CAT activity of tea leaves increased , as the spreading time became longer , the CAT activity decreased until 100 U /g and hold for a long time .It is concluded that the CAT is one of the key enzymes affected tea tree growth and development . In different growth and development stages , the CAT activity is different in tea tree . The basic regulation is that the CAT activity in tea tree increases under stress but decreases when the stress is extremely severe .