Structural and functional differences among purified recombinant mammalian aromatases: Glycosylation, N-terminal sequence and kinetic analysis of human, bovine and the porcine placental and gonadal isozymes

C. Jo Corbin, S. M. Mapes, Young M. Lee, Alan J Conley

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

Recombinant porcine gonadal and placental, and the human and bovine, isozymes of aromatase cytochrome P450 (P450arom) were over-expressed in insect cells, purified and quantified by difference spectroscopy. Human and bovine P450arom exhibited greater apparent molecular size than either porcine isozyme prompting an examination of N-linked glycosylation and amino-terminal peptide sequence. Comparisons of substrate affinities and turnover were also made. In contrast to human and bovine P450arom which are N-linked glycoproteins, neither isozyme of porcine P450arom is glycosylated, explaining in part their lower molecular size. Differences found in N-terminal peptide sequences were unlikely to influence apparent molecular size or enzyme function. Human and bovine P450arom had similar affinities and turnovers for androstenedione (∼200 nM, 3/min) and testosterone (∼350 nM, 2/min). The porcine isozymes had 10-fold higher affinities but correspondingly lower turnovers, particularly the gonadal P450arom. Overall, the catalytic efficiency (Vmax/Km) was similar for all but porcine gonadal P450arom which was much lower. These data emphasize the structural and functional variability of even the most conserved of proteins among diverse species wherein such differences have previously remained unexpected.

Original languageEnglish (US)
Pages (from-to)147-157
Number of pages11
JournalMolecular and Cellular Endocrinology
Volume206
Issue number1-2
DOIs
StatePublished - Aug 29 2003

Keywords

  • Androgen
  • Aromatase
  • Bovine
  • Difference spectroscopy
  • Estrogen
  • Glycosylation
  • Human
  • Ovary
  • P450
  • Peptide sequence
  • Placenta
  • Porcine

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

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