Quinone Oxidoreductases is not a Selenoprotein.
Selenocysteine (Sec or U or Se-Cys) is the 21st proteinogenic amino acid and is incorporated biosynthetically into the proteins during translation. The amino acid is an analog of cysteine (Cys) with selenium in place of sulfur. The amino acid was first discovered by American biochemist Thressa Campbell Stadtman (1920-2016) at the National Institute of Health in the 1970s. She discovered that the bacterium Clostridium sticklandii needs Selenium ion for the synthesis of enzyme Glycine reductase. The enzyme catalyzes the conversion of glycine to acetate.
Selenoproteins are proteins that contain a selenocysteine amino acid (Sec, Se-Cys) residue. Glutathione Peroxidases, Thioredoxin Reductases, and Selenoprotein P contain Selenocysteine amino acids. The enzyme Quinone Oxidoreductases do not contain any Selenocysteine amino acid.