Retinal biosynthesis in Eubacteria: in vitro characterization of a novel carotenoid oxygenase from Synechocystis sp. PCC 6803.
Retinal and its derivatives represent essential compounds in many biological systems. In animals, they are synthesized through a symmetrical cleavage of beta-carotene catalysed by a monooxygenase. Here, we demonstrate that the open reading frame sll1541 from the cyanobacterium Synechocystis sp. PCC 6803 encodes the first eubacterial, retinal synthesizing enzyme (Diox1) thus far reported. In contrast to enzymes from animals, Diox1 converts beta-apo-carotenals instead of beta-carotene into retinal in vitro. The identity of the enzymatic product was proven by HPLC, GC-MS and in a biological test. Investigations, of the stereospecifity showed that Diox1 cleaved only the all-trans form of beta-apo-8'-carotenal, yielding all-trans-retinal. However, Diox1 exhibited wide substrate specificity with respect to chain-lengths and functional end-groups. Although with divergent Km and Vmax values, the enzyme converted beta-apo-carotenals, (3R)-3-OH-beta-apo-carotenals as well as apo-lycopenals into retinal, (3R)-3-hydroxy-retinal and acycloretinal respectively. In addition, the alcohols of these substrates were cleaved to yield the corresponding retinal derivatives.
Ruch
Sandra
S
Albert-Ludwigs University of Freiburg, Institut for Biology II, Cellbiology, Schaenzlestr. 1, D-79104 Freiburg, Germany.
Beyer
Peter
P
Ernst
Hansgeorg
H
Al-Babili
Salim
S
D000821:Animal Feed; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002338:Carotenoids / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers; D004330:Drosophila / Q000502:physiology; D007700:Kinetics; D016366:Open Reading Frames; D010105:Oxygenases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D012172:Retinaldehyde / Q000096:biosynthesis*; D013379:Substrate Specificity; D046939:Synechocystis / Q000201:enzymology* / Q000235:genetics
D001426:Bacterial Proteins; D017931:DNA Primers; D002338:Carotenoids; D010105:Oxygenases; C500451:carotenoid oxygenase; D012172:Retinaldehyde