tda1 (biosynthetic threonine deaminase, UniProt O94634, SPBC1677.03c) - notes

Identity / NAMING TRAP

• PomBase tda1 = SPBC1677.03c = UniProt O94634 (UniProt has no gene name). It is the ortholog of S. cerevisiae ILV1 (P00927), not of S. cerevisiae TDA1 (an unrelated protein kinase). Conversely S. pombe ilv1 (P36620) is the acetolactate synthase (S. cerevisiae ILV2 ortholog).

Function

• Threonine dehydratase/deaminase EC 4.3.1.19: "Reaction=L-threonine = 2-oxobutanoate + NH4(+); Xref=Rhea:RHEA:22108," [UniProt:O94634]; PLP cofactor; isoleucine inhibits, valine activates (by similarity).
• S. pombe enzyme characterised biochemically [PMID:4698209 "Biosynthetic threonine deaminase (TD) from Schizosaccharomyces pombe has been partially purified from crude extracts"; "TD showed marked stimulation by pyridoxal phosphate"; "the natural feedback inhibitor, l-isoleucine"; "l-Valine was found to reverse isoleucine inhibition"]. This regulatory behaviour matches S. cerevisiae Ilv1. Note this 1973 work used extracts; the assignment of the activity to SPBC1677.03c is by the PomBase curator.

Localization

• Predicted mitochondrial transit peptide (FT TRANSIT 1..?) and Mitochondrion by similarity to P00927 [UniProt:O94634].
• ORFeome HDA: cytoplasm PMID:16823372. Conflicts with the mitochondrial prediction; PomBase also has IC mitochondrial matrix and the GO-CAM places the activity in the matrix.

GO-CAM

• gomodel:6690711d00002706: SPBC1677.03c enables GO:0004794, occurs_in GO:0005759 mitochondrial matrix, part_of GO:1901705 (IDA PMID:4698209 + IBA). No causal edge to AHAS (ilv1).