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J. Biochem, 1988, Vol. 103, No. 6 1054-1059
© 1988 Japanese Biochemical Society

research-article

Quinolinic Acid Phosphoribosyltransferase: Purification and Partial Characterization from Human Liver and Brain1

Etsuo Okuno, Robert J. White and Robert Schwarcz2

Maryland Psychiatric Research Center Baltimore, MD 21228, U.S.A.

2To whom correspondence should be addressed at: Maryland Psychiatric Research Center, P.O. Box 21247, Baltimore, MD 21228, U.S.A.

Quinolinic acid phosphoribosyltransferase (QPRT) [EC 2.4.2.19 [EC] ] from human liver and brain was purified to homogeneity. Identity of the pure enzymes isolated from the two organs was proven by biochemical, physicochemical and, following the production and partial purification of anti-liver QPRT antibodies, immunological techniques. Human QPRT has a molecular weight of 170,000 and consists of five identical subunits. Kinetic analyses revealed a Km of 5.6 µM for the substrate (quinolinic acid) and 23 µM for the co-substrate (phosphoribosylpyrophosphate). Enzyme activity was dependent on Mg2+ (optimal concentration: 1 mM) and was inhibited by the enzymatic by-product, inorganic pyrophosphate. Pure QPRT and its antibodies will constitute useful tools in the examination of the possible role of quinolinic acid in the pathogenesis of human neurodegenerative disorders.

1This work was supported by USPHS grants NS 16102 and NS 20509 and a donation from the Lena Marcus Fund (to R.S.).


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