An improved procedure is reported for the purification of Escherichia coli pyruvate oxidase (pyruvate:ferricytochrome b1 oxidoreductase, EC 18.104.22.168), a peripheral membrane flavo-enzyme, which is much more reproducible and requires considerably less time than the original purification scheme. The key element in this protocol is a new Sepharose-based affinity resin designed for the isolation of thiamine pyrophosphate-requiring enzymes. The synthesis, partial characterization, and use of two such affinity resins is described. Pyruvate oxidase is a pure, homogeneous protein as it is eluted from the affinity resin. The enzyme is a tetramer with a subunit molecular weight of approx. 60 000. The subunits appear to be identical. The isoelectric point of pyruvate oxidase is 5.6.
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