Carotene biosynthesis with isolated photosynthetic membranes

Abstract

There are several cell-free systems from eukaryotic organisms capable of in vitro carotenogenesis. The system from the fungus Phycomyces, converting mevalonic acid (MVA) into /&carotene has been extensively investigated [ 1,2]. A homogenate from Neurospora can synthesize phytoene from MVA and other prenyl pyrophosphates [3,4]. Isolated tomato [5], Narcissus-flower [6], and Cap&urn-fruit [7] chromoplasts are reported to convert isopentenyl pyrophosphate (IPP) into p-carotene and be able to catalyze other reactions along this pathway. Recently, an Amphidinium homogenate has been found to synthesize xanthophylls and P-carotene from MVA [8]. (pH 7.8), [N-tris-(hydroxymethyl)-methyl glycine] with 10 mM MgC12, 2.5 mM NasHP04, 2.5 mM K2HP04, and 0.5 M sucrose. The untreated suspension was diluted lo-fold and washed with either water or 0.4 M Tris-HCl (pH 7.8) [tris-(hydroxymethyl)-amino methane]. Washed suspensions were spun down and the pellet resuspended in 0.4 M Tris-MC1 (pH 7.8), to a chlorophyll concentration of 500 pug/ml (washed thylakoid suspension).