Table 1 Human selenoproteins

Antioxidant enzymes

GPx1^a

Cytosolic glutathione peroxidase (GPx)

Cytosol, mitochondria; widely expressed

GPx2^a

Gastrointestinal GPx

Cytosol, ER; gastrointestinal tissue, liver

GPx3

Plasma GPx

Secreted; plasma, extracellular fluid, liver, kidney, heart, lung, thyroid, gastrointestinal tissue, breast

GPx4^a

Phospholipid hydroperoxide GPx

Cytosol, mitochondria, nucleus; widely expressed, testes

GPx6

Olfactory GPx

Unknown; embryo and oilfactory epithelium

SelK

Selenoprotein K

ER, membrane protein

SelR

Selenoprotein R; methionine sulfoxide reductase B1

Cytosol, nucleus; widely expressed

SelW

Selenoprotein W

Cytosol; widely expressed, brain, colon, heart, skeletal muscle, prostate

Transport and storage of Se

SepP1^a

Selenoprotein P

Secreted, cytosol; plasma, widely expressed, brain, liver, testes

Redox signaling

TrxR1^a

Thioredoxin reductase, type I

Cytosol, nucleus; widely distributed

TrxR2

Thioredoxin reductase, type II

Mitochondria; widely distributed

TrxR3

Thioredoxin reductase, type III

Cytosol, ER, nucleus; testis-specific

Thyroid hormone metabolism

DIO1

Iodothyronine deiodinase, type I

Membrane protein; kidney, liver, thyroid, brown adipose tissue

DIO2

Iodothyronine deiodinase, type II

ER, membrane protein; thyroid, central nervous system, brown adipose tissue, skeletal muscle

DIO3

Iodothyronine deiodinase, type III

Membrane protein; placenta, central nervous system, fetus

Protein folding

Sep15^a

Selenoprotein 15 kDa

ER lumen

SelN

Selenoprotein N

ER membrane; widely expressed

SelM

Selenoprotein M

ER lumen

SelS^a,b

Selenoprotein S

ER, membrane protein; widely expressed

Sec synthesis

SPS2

Selenophosphate synthetase

Cytosol

Unknown

SelH

Selenoprotein H

Nucleus; widely expressed

SelI

Selenoprotein I

Transmembrane

SelO

Selenoprotein O

Unknown

SelT

Selenoprotein T

ER membrane

SelV

Selenoprotein V

Testes