Functional analysis of two solanesyl diphosphate synthases from Arabidopsis thaliana

• Published in: Bioscience, biotechnology, and biochemistry biotechnology, and biochemistry, 2005-03, Vol.69 (3), p.592-601
• Main Authors: Hirooka, K. (Osaka Univ., Suita (Japan)), Izumi, Y, An, C.I, Nakazawa, Y, Fukusaki, E, Kobayashi, A
• Format: Article
• Language: English
• Subjects: Alkyl and Aryl Transferases - chemistry; Alkyl and Aryl Transferases - genetics; Alkyl and Aryl Transferases - metabolism; Amino Acid Sequence; AMINO ACID SEQUENCES; Arabidopsis - enzymology; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; ARABIDOPSIS THALIANA; Base Sequence; BIOCHEMICAL PATHWAYS; Biological and medical sciences; BIOSYNTHESIS; Cell Compartmentation; Cloning, Molecular; DNA Primers; DNA, Complementary; Fundamental and applied biological sciences. Psychology; Green Fluorescent Proteins - genetics; isoprenoid; ISOPRENOIDS; Kinetics; LIGASES; Molecular Sequence Data; nonaprenyl diphosphate; PHOSPHATES; plastoquinone; Polymerase Chain Reaction; prenyltransferase; QUINONES; Recombinant Fusion Proteins - genetics; RECOMBINANT PROTEINS; Sequence Homology, Amino Acid; Substrate Specificity; TRANSFERASES; ubiquinone
• ISSN: 0916-8451; 1347-6947
• DOI: 10.1271/bbb.69.592

Solanesyl diphosphate (SPP) is regarded as the precursor of the side-chains of both plastoquinone and ubiquinone in Arabidopsis thaliana. We previously analyzed A. thaliana SPP synthase (At-SPS1) (Hirooka el al, Biochem. J., 370,679-686 (2003)). In this study, we cloned a second SPP synthase (At-SPS2) gene from A. thaliana and characterized the recombinant protein. Kinetic analysis indicated that At-SPS2 prefers geranylgeranyl diphosphate to farnesyl diphosphate as the allylic substrate. Several of its features, including the substrate preference, were similar to those of At-SPSl. These data indicate that At-SPS1 and At-SPS2 share their basic catalytic machinery. Moreover, analysis of the subcellular localization by the transient expression of green fluorescent protein-fusion proteins showed that At-SPS2 is transported into chloroplasts, whereas At-SPS1 is likely to be localized in the endoplasmic reticulum in the A. thaliana cells. It is known that the ubiquinone side-chain originates from isopentenyl diphosphate derived from the cytosolic mevalonate pathway, while the plastoquinone side-chain is synthesized from isopentenyl diphosphate derived from the plastidial methylerythritol phosphate pathway. Based on this information, we propose that At-SPS1 contributes to the biosynthesis of the ubiquinone side-chain and that At-SPS2 supplies the precursor of the plastoquinone side-chain in A. thaliana.