#12 EC 5.4.3.6 ATP cofactor or substrate?

[Julia Fischer]

I have ordered the only reference for this entry. Although the authors claim in the abstract that ATP is a cofactor for this enzyme, they write on page 6 in the section "Geneal characteristics id beta-tyrosine formation" that they experimentally proved that "in the course og the reaction ATP was cenverted to ADP" which indicates that ATP is rather than a cofactor.

[Kristian Axelsen]

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Dear Julia,

Thank you for also this report. I have not read the original article but I have tried to find more recent literature about the enzyme.

It turns out that one of these enzymes has just been crystallised (see pmid:17516659 and 18052279). In the crystal structure you find no ATP neither as cofactor nor substrate, instead you find the cofactor MIO (4-methylideneimidazole-5-one). This unique cofactor is formed autocatalytically by cyclization and dehydration of the three amino-acid residues alanine, serine and glycine.

Another interesting feature of the enzyme is that it is very similar to the ammonia-lyases such as the ones described in EC 4.3.1.23, EC 4.3.1.24 and EC 4.3.1.25.

So in conclusion, I do not think ATP should be mentioned at all in the entry. I will request an update of the entry by the IUBMB.

Thank you once again for reporting these errors. I hope you will continue, as it is an important help to improve the data quality of the database.

Regards,

Kristian Axelsen

[Julia Fischer]

Is there a reason why this is still not changed in IntEnz? Can you add MIO as a cofactor instead? If so, when?