Studies On Properties Of Some Enzymes Involved In Chlorophyll Degradation And Mechanism Of Degradation

Until very recently, the phenomenon of chlorophyll breakdown in plants was considered as a major biological enigma. Chlase and PaO were two of the most important members of enzymes involved in Chl enzymatic degradation pathway. In order to explore biochemistry mechanism of Chl degradation, two varieties of wheat named LM15 and PH85-16 were selected from some kinds of wheat that were applied in practice. We mainly used PH85-16 as material and LM15 as control to culture seedlings. By treatments of light and dark, we got the following results:Properties of Chlase and PaO from excised leaves were studied. The optimum pH of Chlase was 7.5. The Km value for Chl was about 11.6 u mol/L and the Vmax value for Chl was 1.14 u mol/ (min · g FW) . The optimum temperature of Chlase was about 45 ℃. The half-life of Chlase activities was different at different high temperature. When being incubated at 60 ℃,70℃, 80℃, Chlase could lose its half activities in 21 minutes,22 minutes, 18 minutes. With different Chl, Chlase showed different kinetic properties. Different ions were found having different effects on Chlase activities. At the 4 days the Chlase activities rise up to the maximum In order to study PaO, Fd was prepared. And different methods got different states of Fd. Votive Fd got from spinach by simple method had absorb at 267 and 332nm.And this Votive Fd were used to study PaO. We introduced a method to identify FCC by HPLC. Some properties of PaO from excised wheat leaves were studied. At the temperature about 20 ℃, PaO showedcertain activities The reservation time of FCC was 5.1 minutes The half-life of FCC was 34.66 minutes in without light. PaO activities change smartly during wheat leaves were treated by darkness. At the 5 days the PaO activities rise up to the maximum. The PaO contents had effects on Chl breakdown.Chl contents changed differently in light and dark. And light accelerated the loss of Chl. The loss of Chl a had the same form as loss of total Chl. The loss of Chl b had the different form comparing with loss of Chl a. So the decline of Chl contents was caused by Chl a breakdown. Chl a and Chl b had different breakdown rate. Chl a contents declined smartly and rapidly. Chl b stood steadily. Hormones such as 6 - BA and ABA had different effects on Chl breakdown. ABA accelerated and 6 - BA staved Chl breakdown of attached and detached leaves. The activities of SOD, POD, AsP, CAT and GR changed differently in PH85-16 and LM15. The activities of SOD, POD,AsP, CAT and GR declined at different rate during the course of darkness treatment. The contents of O2- and H2O2 rose up in PH85-16. The contents of O2- and H2O2 of PH85-16 in different shape in light and dark. The activities of SOD, POD, AsP, CAT and GR of PH85-16 changed differently in light and dark. The activities of SOD and CAT lost acutely in light and slowly in dark. Relativity proof - test showed high correlation between Cchl contents and the activities of enzymes and radical.