The activity of rhodanese, 3-mercaptopyruvate sulfurtransferase (MPST) and cystathionase in mouse liver, kidney, and four brain regions: tele-, meso-, di- and rhombencephalon was studied 30 min and 2 h following a sublethal dose of cyanide (4 mg/ kg body weight) intraperitoneal injection. Simultaneously, sulfane sulfur levels and total sulfur content, a direct or indirect source of sulfur for CN⁻ conversion to SCN⁻, were also investigated in these tissues. In the liver this dose of cyanide seemed to impair the process of cyanide detoxification by MPST, as well as rhodanese inhibition. The effects of cyanide administration to mice proved to be totally different in the liver and kidney. In the kidney, a significant increase in the rhodanese activity was observed as early as 30 min following cyanide intoxication, and an elevated cystathionase activity after 2 h was detected. This suggests the involvement of cystathionase in cyanide detoxification in the kidney. The activity of MPST remained at the same level as in the control group. In the rhombencephalon, similarly as in the kidney, L-cysteine desulfuration pathways, which generate sulfane sulfur and sulfurtransferases that transfer sulfane sulfur atoms to CN⁻, seemed to play an important role as a defense system against cyanide. The stable level of sulfane sulfur and total sulfur content was accompanied in the rhombencephalon by an increased activity of MPST, cystathionase and rhodanese. In other brain regions the role of these three sulfurtransferases was not so clear and it seemed that in the telencephalon, where the total sulfur content, but not the sulfane sulfur level, was significantly increased, some sulfur-containing compounds, such as GSH and/or cysteine, appeared in response to cyanide.

We characterized γ-cystathionase, rhodanese and 3-mercaptopyruvate sulfurtransferase activities in various regions of human brain (the cortex, thalamus, hypothalamus, hippocampus, cerebellum and subcortical nuclei) and human gliomas with II to IV grade of malignancy (according to the WHO classification). The human brain regions, as compared to human liver, showed low γ-cystathionase activity. The activity of rhodanese was also much lower and it did not vary significantly between the investigated brain regions. The activity of 3-mercaptopyruvate sulfurtransferase was the highest in the thalamus, hypothalamus and subcortical nuclei and essentially the same level of sulfane sulfur was found in all the investigated brain regions. The investigations demonstrated that the level of sulfane sulfur in gliomas with the highest grades was high in comparison to various human brain regions, and was correlated with a decreased activity of γ-cystathionase, 3-mercaptopyruvate sulfurtransferase and rhodanese. This can suggest sulfane sulfur accumulation and points to its importance for malignant cell proliferation and tumor growth. In gliomas with the highest grades of malignancy, despite decreased levels of total free cysteine and total free glutathione, a high ratio of GSH/GSSG was maintained, which is important for the process of malignant cells proliferation. A high level of sulfane sulfur and high GSH/GSSG ratio could result in the elevated hydrogen sulfide levels. Because of the disappearance of γ-cystathionase activity in high-grade gliomas, it seems to be possible that 3-mercaptopyruvate sulfurtransferase could participate in hydrogen sulfide production. The results confirm sulfur dependence of malignant brain tumors.

Mitochondria are the key organelles of Fe–S cluster synthesis. They contain the enzyme cysteine desulfurase, a scaffold protein, iron and electron donors, and specific chaperons all required for the formation of Fe–S clusters. The newly formed cluster can be utilized by mitochondrial Fe–S protein synthesis or undergo further transformation. Mitochondrial Fe–S cluster biogenesis components are required in the cytosolic iron–sulfur cluster assembly machinery for cytosolic and nuclear cluster supplies. Clusters that are the key components of Fe–S proteins are vulnerable and prone to degradation whenever exposed to oxidative stress. However, once degraded, the Fe–S cluster can be resynthesized or repaired. It has been proposed that sulfurtransferases, rhodanese, and 3-mercaptopyruvate sulfurtransferase, responsible for sulfur transfer from donor to nucleophilic acceptor, are involved in the Fe–S cluster formation, maturation, or reconstitution. In the present paper, we attempt to sum up our knowledge on the involvement of sulfurtransferases not only in sulfur administration but also in the Fe–S cluster formation in mammals and yeasts, and on reconstitution-damaged cluster or restoration of enzyme’s attenuated activity.