RT Journal Article
SR Electronic
T1 mRNA Distribution and Heterologous Expression of Orphan Cytochrome P450 20A1
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 1930
OP 1937
DO 10.1124/dmd.108.022020
VO 36
IS 9
A1 Katarina Stark
A1 Zhong-Liu Wu
A1 Cheryl J. Bartleson
A1 F. Peter Guengerich
YR 2008
UL http://dmd.aspetjournals.org/content/36/9/1930.abstract
AB Cytochrome P450 (P450) 20A1 is one of the so-called “orphan” P450s without assigned biological function. mRNA expression was detected in human liver, and extrahepatic expression was noted in several human brain regions, including substantia nigra, hippocampus, and amygdala, using conventional polymerase chain reaction and RNA dot blot analysis. Adult human liver contained 3-fold higher overall mRNA levels than whole brain, although specific regions (i.e., hippocampus and substantia nigra) exhibited higher mRNA expression levels than liver. Orthologous full-length and truncated transcripts of P450 20A1 were transcribed and sequenced from rat liver, heart, and brain. In rat, the concentrations of full-length transcripts were 3- to 4-fold higher in brain and heart than in liver. In situ hybridization of rat whole brain sections showed an mRNA expression pattern similar to that observed for human P450 20A1, indicating expression in substantia nigra, hippocampus, and amygdala. A number of N-terminal modifications of the codon-optimized human P450 20A1 sequence were prepared and expressed in Escherichia coli, and two of the truncated derivatives showed characteristic P450 spectra (200–280 nmol of P450/l). Although the recombinant enzyme system oxidized NADPH, no catalytic activity was observed with the heterologously expressed protein when a number of potential steroids and biogenic amines were surveyed as potential substrates. The function of P450 20A1 remains unknown; however, the sites of mRNA expression in human brain and the conservation among species may suggest possible neurophysiological function. The American Society for Pharmacology and Experimental Therapeutics