TKFC (triokinase and FMN cyclase) encodes a bifunctional enzyme with dual catalytic activities: triokinase activity that phosphorylates glyceraldehyde and dihydroxyacetone in fructose metabolism, and FMN cyclase activity that cleaves FAD to generate cyclic FMN 1. The enzyme plays a crucial role in fructose metabolism, where triokinase activity converts glyceraldehyde to glyceraldehyde-3-phosphate, favoring lipogenesis over fructose oxidation 2. TKFC expression is regulated by metabolic transcription factors ChR11 and HNF4α, with refeeding inducing hepatic expression 3. The protein forms dimeric structures with two active sites that undergo conformational changes during substrate binding and catalysis 4. TKFC deficiency causes a rare multisystem disorder characterized by cataracts, developmental delay, cerebellar hypoplasia, liver dysfunction, and potentially fatal cardiomyopathy 15. The disease mechanism likely involves disrupted fructose metabolism leading to toxic by-product accumulation and cataract formation. Additionally, TKFC may regulate innate antiviral immunity through MDA5 pathway suppression, potentially explaining severe viral illness susceptibility in deficient patients 1. Alternative splicing generates tissue-specific TKFC variants with differential expression patterns across organs 6.