Catalase as a sulfide-sulfur oxido-reductase: An ancient (and modern?) regulator of reactive sulfur species (RSS)

Abstract

Catalase is well-known as an antioxidant dismutating H2O2 to O2 and H2O. However, catalases evolved when metabolism was largely sulfur-based, long before O2 and reactive oxygen species (ROS) became abundant, suggesting catalase metabolizes reactive sulfide species (RSS). Here we examine catalase metabolism of H2Sn, the sulfur analog of H2O2, hydrogen sulfide (H2S) and other sulfur-bearing molecules using H2S-specific amperometric electrodes and fluorophores to measure polysulfides (H2Sn; SSP4) and ROS (dichlorofluorescein, DCF). Catalase eliminated H2Sn, but did not anaerobically generate H2S, the expected product of dismutation. Instead, catalase concentration- and oxygen-dependently metabolized H2S and in so doing acted as a sulfide oxidase with a P50 of 20 mmHg. H2O2 had little effect on catalase-mediated H2S metabolism but in the presence of the catalase inhibitor, sodium azide (Az), H2O2 rapidly and efficiently expedited H2S metabolism in both normoxia and hypoxia suggesting H2O2 is an effective electron acceptor in this reaction. Unexpectedly, catalase concentration-dependently generated H2S from dithiothreitol (DTT) in both normoxia and hypoxia, concomitantly oxidizing H2S in the presence of O2. H2S production from DTT was inhibited by carbon monoxide and augmented by NADPH suggesting that catalase heme-iron is the catalytic site and that NADPH provides reducing equivalents. Catalase also generated H2S from garlic oil, diallyltrisulfide, thioredoxin and sulfur dioxide, but not from sulfite, metabisulfite, carbonyl sulfide, cysteine, cystine, glutathione or oxidized glutathione. Oxidase activity was also present in catalase from Aspergillus niger. These results show that catalase can act as either a sulfide oxidase or sulfur reductase and they suggest that these activities likely played a prominent role in sulfur metabolism during evolution and may continue do so in modern cells as well. This also appears to be the first observation of catalase reductase activity independent of peroxide dismutation.

Extended hypoxia‐mediated H2S production provides for long‐term oxygen sensing

“…AzMC was used for all plate reader experiments and MeRho for confocal microscopy as it was more compatible with our instrument. Although dichlorofluorescein (DCF) is a relatively non‐specific fluorophore, it is extensively used in ROS studies and was used in this study for comparison to RSS. All of the fluorophores used in this study are irreversibly activated by either reactive sulphur species (RSS; H 2 S and polysulphides) or ROS.…”

“…non-specific fluorophore, 77 it is extensively used in ROS studies and was used in this study for comparison to RSS. All of the fluorophores used in this study are irreversibly activated by either reactive sulphur species (RSS; H 2 S and polysulphides) or ROS.…”

OxyR senses reactive sulfane sulfur and activates genes for its removal in Escherichia coli

“…Therefore, sulfur metabolism related enzymes had emerged before the oxygen’s era. It is reasonable to speculate that the anti-ROS proteins are derived from anti-sulfane sulfur ones (Olson et al, 2017) . Possibly that is the reason why the anti-ROS network largely overlaps with that of anti-sulfane sulfur.…”

“…The pH was adjusted to 9.3 with 6 M HCl. The obtained product contained a mixture of H 2 S n , where n varies from 2 to 8 (Olson et al, 2017) , but at low concentration and neutral pH, H 2 S 2 is dominant (Bogdándi et al, 2018; Xin et al, 2016) .…”

“…Cystathionine β-synthase and cystathionine γ-lyase produce sulfane sulfur from cystine (Ida et al, 2014) ; 3-mercaptopyruvate sulfurtransferase (3-MST) and cysteinyl-tRNA synthetase (CARS) produce sulfane sulfur from cysteine (Akaike et al, 2017; Nagahara et al, 2018) ; Sulfide:quinone oxidoreductase and superoxide dismutase (SOD) produce sulfane sulfur from H 2 S (Olson et al, 2018; Xin et al, 2016) . Catalase can oxidize H 2 S and polysulfides to sulfur oxides (Olson et al, 2017) . Most microorganisms possess several of these pathways.…”