作　　者： ; ;

机构地区： 华南农业大学

出　　处： 《植物生理学报（0257-4829)》 1993年第2期105-110,共6页

摘　　要： 鸡蛋果叶片细胞质丙酮酸激酶(PK_c)纯化92.6倍.其最适pH为7.2,对热较稳定。PEP的K_m为0.037 mmol/L,ADP的K_m为0.05 mmol/L。ASP、Asn、Cys、α—酮戊二酸和苹果酸均对PK?有轻微的激活作用,但草酸、ATP、CaCl_2则具强烈的抑制作用。 Cytoplasmic pyruvate kinase(PK_c) from Passiflora edulis leaves waspurified 92. 6--fold by several steps in-cluding heat treatment, ammoniumsulfate fractionation, DEAE--Sepharoseand Sephadex G--200 chromatography(Table 1). The PK_c had an optimum pH 7. 2for its activity (Fig. 1). It was heatstable, with no loss in activity afterbeing incubated for 5 min at 50℃. The Michaelis constants for PEPand ADP were 0. 037 mmol/L and 0.05 mmol/L, respectively (Fig. 2).Of the 23 chemicals tested, slight acti-vation of PK_c by Asp, Asn, Cys, α-ketoglutarate and malate and potent in-hibition by oxalate, ATP and CaCl_2 of5 mmol/L were observed (Table 2). Oxalate was a competitive inhibitor ofPK_c with respect to PEP (K_i = 0. 34mmol/L) (Fig. 3). ATP was a com-petitive inhibitor with respect to ADP(K_i = 0. 33 mmol/L ), but a mixed-type inhibitor with respect to PEP(Fig. 4, 5). An inhibition of 10%was caused by 0. 01 mmol/L oxalate atthe K_m concentration of PEP and by0. 2 mmol/L ATP at saturating sub-strate concentrations. The results indi-cated that the activity of PK_c in leafcells was probably regulated by the cy-tosolic levels of oxalate, ATP andADP.

关 键 词： 鸡蛋果 叶片 细胞质 丙酮酸激酶

领　　域： [农业科学] [农业科学]