Résumé
The protomeric chain of
Hansenula anomala
flavocytochrome
b
2
was previously shown to be built as the covalent association of two functional domains: an
l
‐Lactate dehydrogenase domain and a cytochrome
c
reductase domain, joined together by a proteolytically sensitive zone. This paper concerns the specific cleavage of this latter zone with a
H. anomala
proteinase(s) preparation and the purification of the purification of the resulting
l
‐lactate: dehydrogenase moiety of the molecule with at least 25% recovery, (i.e. one order of magnitude more than for the previously published method). A preliminary characterization of this dehydrogenase domain indicates that it is a tetramer (
M
r
= 4 × 39000) containing FMN as expected and not heme. It has high
l
‐lactate:ferricyanide oxidoreductase activity (about 70% that of the whole flavocytochrome
b
2
, but it has no
l
‐lactate:cytochrome
c
oxidoreductase activity. Its flavin semiquinone is stabilized in the presence of pyruvate as in flavocytochrome
b
2
. The subcellular origin of the
H. anomala
proteinase in the preparation has not yet been elucidated.