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J Bioenerg Biomembr. 2012 Jun;44(3):333-40. doi: 10.1007/s10863-012-9445-0. Epub 2012 May 4.

The peroxisomal NAD+ carrier of Arabidopsis thaliana transports coenzyme A and its derivatives.

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Department of Biosciences, Biotechnology and Pharmacological Sciences, University of Bari, Via Orabona 4, 70125 Bari, Italy.


The peroxisomal protein PXN encoded by the Arabidopsis gene At2g39970 has very recently been found to transport NAD+, NADH, AMP and ADP. In this work we have reinvestigated the substrate specificity and the transport properties of PXN by using a wide range of potential substrates. Heterologous expression in bacteria followed by purification, reconstitution in liposomes, and uptake and efflux experiments revealed that PNX transports coenzyme A (CoA), dephospho-CoA, acetyl-CoA and adenosine 3', 5'-phosphate (PAP), besides NAD+, NADH, AMP and ADP. PXN catalyzed fast counter-exchange of substrates and much slower uniport and was strongly inhibited by pyridoxal 5'-phosphate, bathophenanthroline and tannic acid. Transport was saturable with a submillimolar affinity for NAD+, CoA and other substrates. The physiological role of PXN is probably to provide the peroxisomes with the essential coenzymes NAD+ and CoA.

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