Enzymatic hydrogen sulfide production in marine invertebrate tissues

At least some mammalian tissues produce H S in vitro from L-cysteine at rates sufficient to have physiological effects. 2 To determine whether tissues of macrofaunal invertebrates have the same capacity, we measured H S production in tissue 2 homogenates of the Manila clam Tapes philippinarum and the lugworm Arenicola marina. Tissue homogenates from both animals produced significant quantities of H S gas upon addition of L-cysteine and the enzyme cofactor pyridoxal- 2 ?-phosphate (10 mmol l and 2 mmol l , respectively), while only tissues from T. philippinarum produced measurable y1 y1 2 by the cystathionine b-synthase (CBS) inhibitor aminooxyacetic acid (AOAA), suggesting that the majority of H S 2 production was via CBS pathways, while in A. marina body wall, AOAA inhibited only half of the total H S production, 2 indicating that the CBS pathway was not the only major source of H S production. H S production in tissues of T. 22 philippinarum but not A. marina was doubled by the addition of a second thiol substrate (2.5 mmol l 2- y1