Linked Life Data

8354284

Source:http://linkedlifedata.com/resource/pubmed/id/8354284

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
3
pubmed:dateCreated
1993-9-17
pubmed:abstractText
Incubation of phosphorylase with L-valine in the presence of 0.4 M imidazole citrate results in a time-dependent decrease in the absorption of the enzyme-bound cofactor pyridoxal 5'-phosphate at 333 nm and the generation of a new absorption maximum at 415 nm which appears to be due to an enzyme-bound coenzyme-amino-acid aldimine adduct. Consequently, the enzyme is inactivated to less than 10% of its initial activity. The formation of the adduct of phosphorylase b with L-valine (0.1 M) proceeds with t1/2 approximately 8 min at pH 6.8 and 25 degrees C and is slightly inhibited by AMP. Phosphorylase a reacts five times more slowly than phosphorylase b. The decrease in enzymic activity is linked to the formation of the coenzyme-amino-acid adduct and is not due to resolution of the enzyme. Both the original absorption spectrum and phosphorylase activity are restored by gel filtration in the absence of L-valine and imidazole citrate. Similar reactions occur with other L-amino acids, an exception being L-cysteine which leads to resolution of the enzyme [Shaltiel, S., Hedrick, J. L. & Fischer, E. H. (1966) Biochemistry 5, 2108-2116]. No reaction is observed with D-amino acids or in the absence of imidazole citrate. Pyridoxal-reconstituted phosphorylase rapidly produces with amino acids not only the aldimine adduct but also a species absorbing at 318 nm. Enzyme-bound pyridoxal 5'-phosphate and pyridoxal exhibit a positive CD signal in the region of 333 nm; in contrast, the absorption bands of the coenzyme-amino-acid adducts at 415 nm and 318 nm are optically inactive. Neither pyridoxal-5'-phosphate-reconstituted nor pyridoxal-reconstituted phosphorylase in imidazole citrate catalyses any of the common pyridoxal-5'-phosphate-mediated reactions of amino acids, e.g. transamination, decarboxylation or racemization, thus testifying to the high degree of reaction specificity of phosphorylase.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Aug
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
215
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
761-6
pubmed:dateRevised
2007-7-23
pubmed:meshHeading
pubmed:year
1993
pubmed:articleTitle
Reaction of imidazole-citrate-deformed glycogen phosphorylase with amino acids.
pubmed:affiliation
Biochemisches Institut der Universität Zürich, Switzerland.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't