Fungal heme oxygenases: Functional expression and characterization of Hmx1 from Saccharomyces cerevisiae and CaHmx1 from Candida albicans

Donghak Kim, Erik T. Yukl, Pierre Moenne-Loccoz, Paul R. Ortiz De Montellano

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Abstract

Heme oxygenases convert heme to free iron, CO, and biliverdin. Saccharomyces cerevisiae and Candida albicans express putative heme oxygenases that are required for the acquisition of iron from heme, a critical process for fungal survival and virulence. The putative heme oxygenases Hmx1 and CaHmx1 from S. cerevisiae and C. albicans, respectively, minus the sequences coding for C-terminal membrane-binding domains, have been expressed in Escherichia coli. The C-terminal His-tagged, truncated enzymes are obtained as soluble, active proteins. Purified ferric Hmx1 and CaHmx1 have Soret absorption maxima at 404 and 410 nm, respectively. The apparent heme binding Kd values for Hmx1 and CaHmx1 are 0.34 ± 0.09 μM and 1.0 ± 0.2 μM, respectively. The resonance Raman spectra of Hmx1 reveal a heme binding pocket similar to those of the mammalian and bacterial heme oxygenases. Several reductants, including ascorbate, yeast cytochrome P450 reductase (CPR), human CPR, spinach ferredoxin/ferredoxin reductase, and putidaredoxin/putidaredoxin reductase, are able to provide electrons for biliverdin production by Hmx1 and CaHmx1. Of these, ascorbate is the most effective reducing partner. Heme oxidation by Hmx1 and CaHmx1 regiospecifically produces biliverdin IXα. Spectroscopic analysis of aerobic reactions with H2O2 identifies verdoheme as a reaction intermediate. Hmx1 and CaHmx1 are the first fungal heme oxygenases to be heterologously overexpressed and characterized. Their heme degradation activity is consistent with a role in iron acquisition.

Original languageEnglish (US)
Pages (from-to)14772-14780
Number of pages9
JournalBiochemistry
Volume45
Issue number49
DOIs
StatePublished - Dec 12 2006

Fingerprint

Heme Oxygenase (Decyclizing)
Candida
Candida albicans
Heme
Yeast
Saccharomyces cerevisiae
Biliverdine
Ferredoxins
NADPH-Ferrihemoprotein Reductase
Iron
Reaction intermediates
Spectroscopic analysis
Spinacia oleracea
Reducing Agents
Carbon Monoxide
Escherichia coli
Virulence
Raman scattering
Yeasts
Electrons

ASJC Scopus subject areas

  • Biochemistry

Cite this

Fungal heme oxygenases : Functional expression and characterization of Hmx1 from Saccharomyces cerevisiae and CaHmx1 from Candida albicans. / Kim, Donghak; Yukl, Erik T.; Moenne-Loccoz, Pierre; Ortiz De Montellano, Paul R.

In: Biochemistry, Vol. 45, No. 49, 12.12.2006, p. 14772-14780.

Research output: Contribution to journalArticle

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