. 2023 Jan 27;60:102617. doi: 10.1016/j.redox.2023.102617

Table 2.

Classification of trace metal and metalloprotein functions [54].

Function	Metal	Representative proteins
Transport and storage of small molecules (mainly O₂)	Fe (heme)	hemoglobin (Hb), myoglobin (Mb), hemerythrin (marine worms), hemocyanin (molluscs, crustaceans, spiders)
	Fe (non-heme)
	Cu
Catalysis – Metalloenzymes
a) redox catalysis, electron transfer	Fe(II)/Fe(III)	catalase (CAT), superoxide dismutase (SOD1), cytochrome c oxidase (CcO), heme peroxidases: myeloperoxidase (MPO), lactoperoxidase (LPO), eosinophil peroxidase (EPO), thyroid peroxidase (TPO)
	Cu(I)/Cu(II)
	(Mn, Co, Mo)
b) acid-base catalysis, hydrolytic reactions	Zn (Ca, Mg, Mn)	carbonic anhydrase (CA), carboxypeptidase A (CPA)
Conformational stabilization of macromolecules
a) metalloenzymes, metal is not in the active site	Zn	alcohol dehydrogenase (ADH5), (1 Zn at the active site and 1 structural), superoxide dismutase (SOD1), prolyl hydroxylase (PHD)
b) structural	Zn	zinc finger proteins
Transport and storage of trace elements	Fe	ferritin, transferrin ceruloplasmin, metallothionein, respective transport proteins of trace elements
Transport and storage of trace elements	Cu
Electron carriers
a) cytochromes	Fe (heme)	cytochrome c, cytochrome P450 (CYPs)
b) iron-sulfur clusters (ISCs)	Fe (non-heme)	Ferredoxins, high potential iron-sulfur proteins (HiPIP)
c) blue copper proteins	Cu	tyrosinase (human), hemocyanin (see O₂ transport)