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J. Biol. Chem., Vol. 265, Issue 17, 9857-9863, Jun, 1990

Heterogeneity among the flavin-containing NADH peroxidases of group D streptococci. Analysis of the enzyme from Streptococcus faecalis ATCC 9790

H Miller, LB Poole and A Claiborne
Department of Biochemistry, Wake Forest University Medical Center, Winston-Salem, North Carolina 27103.

Polyclonal antisera prepared against the purified NADH peroxidase from Streptococcus faecalis ATCC 9790 (Enterococcus hirae) do not cross- react with the ATCC 11700 enzyme. Comparative tryptic maps of the two proteins indicate that the differences in primary structures extend beyond those localized to respective antigenic epitopes. Alignments of the NH2-terminal and active-site cysteinyl peptide sequences of the two streptococcal peroxidases reveal identities of 50 and 67% in the respective overlap regions. Dithionite titrations of the ATCC 9790 enzyme reveal a separation in potentials (E2 - E1) for the nonflavin and flavin redox centers of 39 mV, a value nearly 50 mV lower than that observed with the ATCC 11700 peroxidase. Despite these changes in redox behavior NADH titrations of the ATCC 9790 enzyme give rise to both EH2 and EH2.NADH species as previously observed. The enzyme turnover number with hydrogen peroxide is approximately 60% that of the ATCC 11700 peroxidase; the ATCC 9790 peroxidase is also inhibited during turnover with ethyl hydroperoxide. These findings suggest that the flavoprotein NADH peroxidases may exhibit greater diversity among the group D streptococci than previously observed with the widely distributed enzymes of the related flavoprotein disulfide reductase class.
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