| Abstract: | Phosphoenolpyruvate carboxylase (PEPC) was isolated from leavesof Mesembryanthemum crystallinum, which performed Crassulaceanacid metabolism. PEPC was much more stable when extracted from expanded thanfrom expanding leaves. The inactivation of PEPC in desaltedextracts from expanding leaves was much faster at 25 than at0 °C, was stimulated by raising Mg2+ from 0.1 to 3.0 mM,and was reduced by bovine serum albumin. The same type of inactivationwas found after mixing extracts from the two types of leaves,and the decrease in PEPC activity then also included inactivationof the ’stable’ PEPC from the expanded leaves. Afterelution from DEAE-cellulose, PEPC from expanding leaves wasmuch more stable than in desalted, crude extracts. It is suggested that another enzyme is involved in this inactivationof PEPC, but this needs verification. |
