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Tryptophansynthase in Phycomyces blakesleeanus Teil I: Eigenschaften des Enzyms
Author(s) -
HILGENBERG WILLY,
HOFMANN FRIEDER
Publication year - 1977
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1977.tb04054.x
Subject(s) - phycomyces blakesleeanus , tryptophan synthase , tryptophan , indole test , phycomyces , pyridoxal phosphate , chemistry , stereochemistry , serine , enzyme , biochemistry , cofactor , amino acid , mutant , gene
Tryptophan synthase in Phycomyces blakesleeanus. Part I: Characterization of the enzyme . Tryptophan synthase was tested in light grown 5 days old cultures of Phycomyces blakesleeanus . The test was carried out only by reaction 3 (indole + serine → tryptophan + water) of the tryptophan synthase. The K m values for the substrates indole and serine were found to be 1.3 × 10 ‐4 M and 1.0 × 10 ‐2 M . Two K m values (1.5 × 10 ‐8 M and 1.0 × 10 ‐6 M ) for pyridoxal 5′‐phosphate could be calculated from a Lineweaver‐Burk plot. The transformation of the Lineweaver‐Burk plot into the Hill plot resulted in a straight line with a rise of 0.35 for pyridoxal 5′‐phosphate. At higher concentrations the end product tryptophan and indole‐3‐acetic acid inhibit the tryptophan synthase in vitro .