<p>One member of this family, as characterised in <taxon tax_id="577">Klebsiella terrigena</taxon> [<cite idref="PUB00017788"/>], is able to interconvert acetoin + NADH with meso-2,3-butanediol + NAD(+). It is also capable of irreversible reduction of diacetyl with NADH to acetoin. There has been a reuctance to classify the enzyme as either <db_xref db="EC" dbkey="1.1.1.4"/>, which is (R,R)-butanediol dehydrogenase, or <db_xref db="EC" dbkey="1.1.1.5"/>, which is acetoin dehydrogenase without a specified stereochemistry [<cite idref="PUB00017788"/>]. Another member of this family, from <taxon tax_id="1718">Corynebacterium glutamicum</taxon> (Brevibacteriumflavum), is called L-2,3-butanediol dehydrogenase [<cite idref="PUB00016700"/>].</p><p>This enzyme is a homotetramer in the family of short chain dehydrogenases(<db_xref db="INTERPRO" dbkey="IPR002198"/>). </p>