Falcon deep research report on S. pombe sou1 (SPAC8E11.10 / Q9Y6Z9)
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The "sorbose reductase / sorbitol utilization protein" function of S. pombe
Sou1 is an inference: no direct enzymatic assay, substrate panel, kinetics,
or cofactor-preference measurement for SPAC8E11.10 / Q9Y6Z9 was found in the
retrieved primary literature.
"No direct experimental evidence for the enzymatic reaction, substrate specificity, kinetics, or cofactor preference of the *S. pombe* Sou1 protein was identified in the retrieved full texts."
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The reaction assignment for SOU1-type enzymes (EC 1.1.1.289, L-sorbose to
D-sorbitol) is supported by comparative-genomics annotation rather than by
direct S. pombe characterization.
"Comparative genomics literature also explicitly defines **SOU1 (EC 1.1.1.289)** as converting **L-sorbose → D-sorbitol**"
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The NADPH-dependent L-sorbose reductase biochemistry was demonstrated for the
Candida albicans SOU1 ortholog, not for the S. pombe protein; the SOU1/sou1
symbol is ambiguous across fungi, so cross-organism conflation is a risk.
"“SOU1/sou1” is also used in other fungi (notably *Candida albicans*), where it clearly denotes a sorbose-utilization gene encoding an NADPH-dependent L-sorbose reductase"
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sou1 is a bona fide S. pombe transcript name documented in peer-reviewed work
(analyzed at the expression level in a TFIIH/CDK-activating-kinase study), even
though that work does not establish its biochemical function.
"the gene symbol **sou1** is indeed used for an *S. pombe* transcript in peer-reviewed work"
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No subcellular localization data exist for S. pombe Sou1; any cytosolic
assignment is a family-based inference, not a directly demonstrated location.
"any cytosolic assignment would be a **family-based inference**, not directly demonstrated here"
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Sou1 belongs to the SDR superfamily of NAD(P)(H)-dependent oxidoreductases,
supporting the broad oxidoreductase activity assignment independent of the
specific substrate.
"SDR enzymes are a large superfamily of NAD(P)(H)-dependent oxidoreductases"