tumor-associated hydroquinone oxidase; tNOX; cytosolic ovarian carcinoma antigen 1; APK1 antigen [Includes: Hydroquinone [NADH] oxidase; Protein disulfide-thiol oxidoreductase] (COVA1, ENOX2)
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Function
- role in cell growth
- terminal oxidase of plasma electron transport from cytosolic NADPH via hydroquinones to acceptors at the cell surface
- hydroquinone oxidase activity alternates with a protein disulfide-thiol oxidoreductase activity
- facilitates physical membrane displacements associated with vesicle budding or cell enlargement
- activities oscillate with a period of 22 minutes & play a role in control of the ultradian cellular biological clock
- inhibited by antitumor sulfonylurea LY181984, vabilloid capsaicin, & retinoids
Structure
- glycosylated
- contains 1 RRM domain (RNA recognition motif)
Compartment
extracellular (cancer) & plasma membrane-associated
Alternative splicing
named isoforms=2
Pathology
- found in the sera of cancer patients (wide variety)
- not found in serum of healthy volunteers or patients with disorders other than cancer
- shed into serum by cancer cells (putative)
- expressed on the cell borders of renal carcinoma & ovarian carcinoma, but not on the borders of surrounding non-cancerous stromal cells
- several properties associated with prions including
- resistance to proteases
- resistance to cyanogen bromide digestion
- ability to form amyloid filaments resembling those of spongiform encephalopathies