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  • 1995-1999  (2)
  • Enzymatic sequencing  (1)
  • Key words:Δ5-3β-Hydroxysteroid dehydrogenase  (1)
  • 1
    ISSN: 1432-2048
    Keywords: Key words:Δ5-3β-Hydroxysteroid dehydrogenase ; Δ5-Δ4-Ketosteroid isomerase ; Pregnenolone ; Proges-terone ; Short-chain dehydrogenase/reductases ; Digitalis (cardenolide biosynthesis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Δ5-3β-Ηydroxysteroid dehydrogenase (Δ5-3β-HSD; EC 1.1.1.145), an enzyme converting pregn-5-ene-3β-ol-20-one (pregnenolone) to pregn-5-ene-3,20-dione (isoprogesterone), was isolated from the soluble fraction of suspension-cultured cells of Digitalis lanata L. strain VIII. Starting with acetone dry powder the enzyme was purified in three steps using column chromatography on Fractogel-TSK DEAE, hydroxyapatite and Sephacryl G-200. Fractions with highest Δ5-3β-HSD activity were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After in-situ digestion the resulting bands were sequenced N-terminally. The 29-kDa band yielded three fragments with high sequence homology to members of the superfamily of short-chain dehydrogenases/reductases. High similarity was found to microbial hydroxysteroid dehydrogenases. The band may therefore represent the Δ5-3β-HSD. The purified enzyme was characterized with respect to kinetic parameters, substrate specificity and localization. The function of the enzyme in steroid metabolism is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0173-0835
    Keywords: Matrix assisted laser desorption ; ionization - mass spectrometry ; Suppression effects ; Enzymatic sequencing ; Peptide sequencing ; Ladder sequencing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The techniques of enzymatic and chemical peptide ladder sequencing, coupled with ultraviolet - matrix assisted laser desorption/ionization - mass spectrometry (UV-MALDI-MS) have been improving continuously in the last five years and have now become important tools for primary structure identification. In this work, signal suppression effects, appearing in UV-MALDI-MS (excitation 337 nm) of ladder peptides, were investigated using the 17-amino acid peptide dynorphin A. We show, with examples of simple “two-peptide” systems and more complex “multi-peptide” systems, that suppression effects do in fact exist. The magnitude of the observed suppression is strongly dependent upon both the nature and the amount of the suppressing peptide. Suppression behavior of individual ladder peptides was investigated on equimolar mixtures of ten ladder peptides. Significant signal suppression was recorded for all ladder peptides, with some of them being approximately 170 times lower in signal intensity than the pure, i.e., unsuppressed peptide at the same concentration. For the investigated system  -  dynorphin A, 4-hydroxy-α-cyanocinnamic acid (4-HCCA) matrix, UV excitation  -  a correlation between the extent of suppression and an intractable combination of peptide hydrophobicity and the presence of several basic amino acids can be seen.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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