摘要
植物半胱氨酸合成酶(Cysteine synthase,CSase)和β-氰基丙氨酸合成酶(β-cyanoalanine synthase,β-CAS)分别催化合成半胱氨酸(Cysteine,Cys)和β-氰基丙氨酸(β-Cyanoalanine,β-CA),它们在功能上冗余。本研究以山黧豆、苜蓿和玉米为主要材料,结合电泳对8种常见植物CSase和β-CAS粗酶活性进行了分析。结果表明,检测CSase活性时,8种植物两类粗酶的最适反应时间均为10min,最适pH均为8.0,底物O-乙酰-丝氨酸和Na2S最适浓度分别是10和5 mmol·L-1。检测β-CAS活性时,8种植物两类粗酶的最适反应时间均为30min,最适pH均在9~10范围内,底物Cys最适浓度均为3mmol·L-1,而底物KCN最适浓度前者为80mmol·L-1,后者为3mmol·L-1。8种植物中,CSase活性在种、种内组织间差别不是很大,但β-CAS活性则相反,尤其在茎叶和根中差别较大。
Cysteine synthase(CSase)andβ-cyanoalanine synthase(β-CAS)catalyze the synthesis of cysteine(Cys)andβ-Cyanoalanine(β-CA)in plants,respetively.They have been shown to be functional redundancy.In this study,by combining with native-polyacrylamide gel electrophoresis(native-PAGE),the activities of crude CSase andβ-CAS in eight common plant species were assayed mainly for the examples from grass pea(Lathyrus sativus L),alfalfa(Medicago sativa L)and corn(Zea mays).The results showed that CSase activity could be analyzed through the reaction of strongly acidic ninhydrin with an enzyme product(Cys),and the assays were performed under optimal conditions in which the content of the substrates was 10mmol·L-1 OAS and 5mmol·L-1 Na2 S for both enzymes,with pH 8and 10 min of reaction time in eight plants.For the activity ofβ-CAS,it could be determined by using reaction of strongly acidic DMPDA with an enzyme product(H2S).The enzymatic reaction was initiated by mixture of crude protein supernatant with the optimum content of the substrates(3mmol·L-1 cysteine,3mmol·L-1 KCN forβ-CAS,or80mmol·L-1 KCN for CSase,pH 9~10),continued for 30 min in eight plants.No significant differences for CSase activities were found among species and different tissues of the same species in eight plants,however,forβ-CAS activities the opposite patterns were observed especially in stems,leaves and roots.
出处
《氨基酸和生物资源》
CAS
2014年第4期66-72,共7页
Amino Acids & Biotic Resources
基金
国家自然科学基金项目(31160060
31260568)
