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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Crop Improvement and Genetics Research » Research » Publications at this Location » Publication #166938
Title: REGULATION OF RUBBER BIOSYNTHETIC RATE AND MOLECULAR WEIGHT IN HEVEA BRASILIENSIS BY METAL COFACTOR

Author
item DA COSTA, BERNARDO - UNIV OF CA, BERKELEY
item KEASLING, JAY - UNIV OF CA, BERKELEY
item Cornish, Katrina

Submitted to: Biomacromolecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/22/2004
Publication Date: 12/2/2004
Citation: Da Costa, B.M., Keasling, J.D., Cornish, K. 2004. Regulation of rubber biosynthetic rate and molecular weight in hevea brasiliensis by metal cofactor. Biomacromolecules. Vol. 6, No.1, 279-289.

Interpretive Summary: Natural rubber is a strategic raw material used in at leasst 40,000 different items. As domestic rubber-producing crops develop it is important to understand how rubber yield (related to the number of molecules and the biosynthetic rate) and quality (rubber molecular weight) are regulated by plants. In this study, the role of metal cofactor is investigated in the Brazilian rubber tree. The number of rubber molecules, the rate of rubber biosynthesis and the molecular weight of the polymers produced in vitro are strongly affect by metal concentration as well as by the concentration of initiating and elongating substrates. Metal also directly affects the affinity of the rubber enzyme for the substrates and high levels of metal proved inhibitory. The results suggest that the rubber tree may use metal concentration as a regulatory mechanism for rubber biosynthesis.

Technical Abstract: Metal cofactors are necessary for prenyltransferase enzymes. Magnesium and manganese can be used as metal cofactor by rubber transferase (a cis-prenyltransferase) associated with purified rubber particles. The rubber initiation rate, biosynthetic rate and molecular weight produced in vitro from Hevea brasiliensis rubber transferase is regulated by [metal]. In addition, KmIPP.Mg varies significantly with [Mg2+]. Decreasing from 8000±600?M at [Mg2+] = 4mM to 68±10?M at [Mg2+] = 8mM and increasing back to 970±70?M at [Mg2+] = 30mM. The highest affinity of rubber transferase for IPP.Mg occurred when [Mg2+] = Amax (metal concentration that gives highest IPP Incorporation Rate). A metal is required for rubber biosynthesis, but an excess of metal ions interacts with the rubber transferase inhibiting its activity. The results suggest that H. brasiliensis could use [Mg2+] as a regulatory mechanism for rubber biosynthesis and molecular weight in vivo.