Cystathionine β-synthase and cystathionine γ-lyase in tissues of the nemertean <i>Cerebratulus marginatus</i> Renier, 1804 (Nemertea)
Using immunohistochemistry, we have examined the distribution of the hydrogen sulfide (H <sub>2</sub>S) synthesizing enzymes cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) in tissues of the nemertean Cerebratulus marginatus Renier, 1804 (Heteronemertea: Lineidae). The expression of both CBS and CSE was found in the body wall and in the receptor cells of the canals of the cerebral organs; the expression of CBS, in the foregut and intestine; CSE, in the brain, lateral nerve cords, and cerebral organs. The peculiarities of distribution and the possible functional role of H <sub>2</sub>S-synthesizing elements in nemerteans are discussed.