Lactoperoxidase catalytically oxidize hydrogen sulfide via intermediate formation of sulfheme derivatives.

The biological chemistry of hydrogen sulfide (HS) with physiologically important heme proteins is in the focus of redox biology research. In this study, we investigated the interactions of lactoperoxidase (LPO) with HS in the presence and absence of molecular dioxygen (O) or hydrogen peroxide (HO). Under anaerobic conditions, native LPO forms no heme-HS complex upon sulfide exposure.

Bioinformatic Characterization and Molecular Evolution of the Hemoglobins.

(1) Introduction: is a clam found in sulfide-rich mud environments that has three hemoglobins believed to be responsible for the transport of hydrogen sulfide (HbI) and oxygen (HbII and HbIII) to chemoautotrophic endosymbionts. The physiological roles and evolution of these globins in sulfide-rich environments are not well understood. (2) Methods: We performed bioinformatic and phylogenetic analyses with 32 homologous mollusk globin sequences.

Fluoride binding to characteristic heme-pocket centers: Insights into ligand stability.

The studies on the L. pectinata hemoglobins (HbI, HbII, and HbIII) are essential because of their biological roles in hydrogen sulfide transport and metabolism. Variation in the pH could also play a role in the transport of hydrogen sulfide by HbI and oxygen by HbII and HbIII, respectively.

SAXS structure of homodimeric oxyHemoglobin III from bivalve Lucina pectinata.

Hemoglobin III (HbIII) is one of the two oxygen reactive hemoproteins present in the bivalve, Lucina pectinata. The clam inhabits a sulfur-rich environment and HbIII is the only hemoprotein present in the system which does not yet have a structure described elsewhere. It is known that HbIII exists as a heterodimer with hemoglobin II (HbII) to generate the stable Oxy(HbII-HbIII) complex but it remains unknown if HbIII can form a homodimeric species.

Lucina pectinata oxyhemoglobin (II-III) heterodimer pH susceptibility.

Lucina pectinata live in high concentrations of hydrogen sulfide (HS) and contains one hemoglobin, Hemoglobin I (HbI), transporting HS and two hemoglobins, Hemoglobin II (HbII) and Hemoglobin (HbIII), transferring dioxygen to symbionts. HbII and HbIII contain B10 tyrosine (Tyr) and E7 glutamine (Gln) in the heme pocket generating an efficient hydrogen bonding network with the (HbII-HbIII)-O species, leading to very low ligand dissociation rates. The results indicate that the oxy-hemeprotein is susceptible to pH from 4 to 9, at acidic conditions, and as a function of the potassium ferricyanide concentration, 100% of the met-aquo derivative is produced.