Pigment-free NADPH:protochlorophyllide oxidoreductase from Avena sativa L. Purification and substrate specificity.
Eur J Biochem
; 265(3): 862-74, 1999 Nov.
Article
en En
| MEDLINE
| ID: mdl-10518779
The enzyme NADPH:protochlorophyllide oxidoreductase (POR) is the key enzyme for light-dependent chlorophyll biosynthesis. It accumulates in dark-grown plants as the ternary enzyme-substrate complex POR-protochlorophyllide a-NADPH. Here, we describe a simple procedure for purification of pigment-free POR from etioplasts of Avena sativa seedlings. The procedure implies differential solubilization with n-octyl-beta-D-glucoside and one chromatographic step with DEAE-cellulose. We show, using pigment and protein analysis, that etioplasts contain a one-to-one complex of POR and protochlorophyllide a. The preparation of 13 analogues of protochlorophyllide a is described. The analogues differ in the side chains of the macrocycle and in part contain zinc instead of the central magnesium. Six analogues with different side chains at rings A or B are active substrates, seven analogues with different side chains at rings D or E are not accepted as substrates by POR. The kinetics of the light-dependent reaction reveals three groups of substrate analogues with a fast, medium and slow reaction. To evaluate the kinetic data, the molar extinction coefficients in the reaction buffer had to be determined. At concentrations above 2 mole substrate/mole enzyme, inhibition was found for protochlorophyllide a and for the analogues.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Oxidorreductasas
/
Avena
/
Oxidorreductasas actuantes sobre Donantes de Grupo CH-CH
Idioma:
En
Revista:
Eur J Biochem
Año:
1999
Tipo del documento:
Article
País de afiliación:
Alemania
Pais de publicación:
Reino Unido