Abstract
The flavoenzymes dimethylglycine dehydrogenase (EC 1.5.99.2) and sarcosine dehydrogenase (EC 1.5.99.1) contain covalently bound FAD linked via the 8 alpha-position of the isoalloxazine ring to the imidazole N(3) of a histidine residue (Cook, R. J., Misono, K. S., and Wagner, C. (1984) J. Biol. Chem. 259, 12475-12480). The flavin-peptides from tryptic digests of these two enzymes have been isolated and sequenced. Automated sequence analysis showed that the flavin-peptide from dimethylglycine dehydrogenase contained 25 amino acid residues in the following sequence: Ser-Glu-Leu-Thr-Ala-Gly-Ser- Thr-Trp-His(flavin)-Ala-Ala-Gly-Leu-Thr-Thr-Tyr-Phe-His-Pro-Gly-Ile-A sn-Leu-Lys. The sequence determined for the flavin-peptide from sarcosine dehydrogenase contained 14 amino acid residues Leu-Thr-Ser-Gly-Thr-Thr-Trp-His(flavin)-Thr-Ala-Gly-Leu-Gly-Arg.
Highlights
From the Departmentof Biochemistry, Vanderbilt University, Nashville, Tennessee 37232 and the Veterans Administration Medical Center, Nashville, Tennessee 37203
The fluorescence of the flavinpeptide is considerably quenched.’. Both dimethylglycine dehydrogenase and sarcosine dehydrogenase contain only one non-heme iron and approximately 0.5 mol of acid-labile sulfur: suggesting that another system in addition to the Fe-S cluster maybe used for transfer of electrons to electrontransfer flavoprotein, which is the natural electron acceptor [21].From the results presented in this paper,the tryptophan residue is in close proximity to the flavin and may act as an electron-conducting system in both enzymes
BValues i n parentheses %ret h e numbers obtainedfromthe sequence 'N.0
Summary
Vol 260, No 24, Issue of October 25, pp. 1299&13002,1985 Printed in U.S.A. The Amino AcidSequences of theFlavin-peptides of Dimethylglycine Dehydrogenase andSarcosine Dehydrogenase from RatLiver Mitochondria*. From the Departmentof Biochemistry, Vanderbilt University, Nashville, Tennessee 37232 and the Veterans Administration Medical Center, Nashville, Tennessee 37203. 8a-position of the isoalloxazine ring to the imidazole N(3) of a histidine residue
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