The role of acidic amino-acid residues in catalytic and adsorptive sites of Bacillus cereus spingomyelinase

Masahiro Tomita, Yasuji Ueda, Hiro omi Tamura, Ryo Taguchi, Hiroh Ikezawa

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


By the modification of acidic amino-acid residues with Woodward's reagent K (N-ethyl-5-phenylisoxazolium-3′-sulfonate), the activity of sphingomyelinase of Bacillus cereus was decreased by 80-90%. Also, the reduction of Cys residues in the sphingomyelinase molecule by dithiothreitol cause a drasic decrease in enzymatic activity, whereas the spingomyelinase activity was not affected by treatment with p-chloromercuribenzenesulfonic acid. Actually, no inactivation of sphingomyelinase activity was observed after selective modification of basic amino-acid residues such as Lys, His and Arg, and of the unchanged amino-acid residues Ser and Thr. The treatment of the sphingomyelinase molecule with Woodward's reagent K or dithiothreitol also brought about the inhibition of the specific adsorption of sphingomyelinase toward intact erythrocyte membranes. However, the extent of inhibition in the enzyme adsorption, 20-50%, was less than that observed in the sphingomyelinase activity. These results suggest that acidic amino-acid residues, such as Asp and Glu, in the sphingomyelinase molecule are involved in the catalytic sites and the adsorptive sites. Apparently, the disruption of disulfide linkage in the sphingomyelinase molecule by dithiothreitol destabilized its structure, resulting in a drastic decrease in sphingomyelin-hydrolyzing activity and specific adsorption of sphingomyelinase towards crythrocyte membranes.

Original languageEnglish
Pages (from-to)85-92
Number of pages8
JournalBiochimica et Biophysica Acta (BBA)/Protein Structure and Molecular
Issue number1
Publication statusPublished - 1993 Nov 10
Externally publishedYes


  • (B. cereus)
  • Amino acid residue, acidic
  • Chemical modification
  • Homologous sequence
  • Sequence analysis
  • Sphingomyelinase

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology


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