Table 1.

Sulfheme formation in different hemeproteins

Protein	Key distal site residues	Sulfheme
Horse heart Mb	His	Yes (618 nm)
Human Hb	His	Yes (620 nm)
L. pectinata HbII and HbIIIa	Gln	No
L. pectinata HbI	Gln	No
HbI Gln64Asnb	Asn	No
HbI Gln64Hisb	His	Yes (624 nm)
HbI Phe29Hisb	Gln	No
HbI Phe68Hisb	Gln	No
HbI Phe29Leub	Gln	No
HbI Gln64Argb	Arg	No
HbI Phe68Valb	Gln	No
Macrobdella decora Hbsc	His	Yes (620 nm)
Lumbricus terrestris Hbsc	His	Yes (620 nm)
Catalase	His	Yes (635 nm)
Lactoperoxidase	His	Yes (638 nm)
Dehaloperoxidased	His	Yes (620 nm)
Horseradish peroxidase	Arg	No
Cytochrome c oxidase	His (cyt a3)	No
Heme-O2 sensor Ec Dos Pas	Met, Arg	No
Ec Dos Pas Met95Alae	Ala	No
Ec Dos Pas Met95Hise	His	No
Ec Dos Pas Met95Leue	Leu	No
Ec Dos Pas Arg97Alae	Ala	No
Ec Dos Pas Arg97Glue	Glu	No
Ec Dos Pas Arg97Ilee	Ile	No

^aHbII and HbIII are O₂ transport proteins found in L. pectinata [8].

^bPoint mutants of HbI from L. pectinata. The numbers represent the position of the amino acid in the polypeptide chain [17, 18].

^cMacrobdella decora and Lumbricus terrestris are invertebrates that live is sulfide-free environments and have large Hbs that transport O₂ [18].

^dThis enzyme is found in the marine worm Amphitrite ornate and is believed to be involved in H₂S catabolism [75].

^ePoint mutants of the heme sensor phosphodiesterase from Escherichia coli (Ec DOS PAS) [86].