An enzymatically inactive factor which binds with antibody to streptococcal nicotinamide adenine dinucleotidase (NADase), possibly an inactive form of NADase or an enzyme precursor, is produced in early streptococcal culture supernatant fluids. A similar factor is found in fully grown culture supernates in the absence of sufficient sulfhydryl compounds. The antibody-combining capacity of this inactive factor and of NADase chemically inactivated by sulfhydryl inhibitors is equivalent to that of active NADase.These findings are of theoretical interest in that the site of enzymatic activity does not appear to be involved in the specificity of the antibody configuration. Of practical concern is the demonstration that the presence of inactive enzyme will result in spurious antibody titers.
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