Linked Life Data

2054157

Source:http://linkedlifedata.com/resource/pubmed/id/2054157

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1991-7-31
pubmed:abstractText
We have examined the effect of glucose and caffeine inhibition on the activity of liver glycogen phosphorylase a from the freeze-tolerant frog Rana sylvatica. Kinetic studies indicate that this enzyme exhibits similar sensitivity to glucose inhibition (glucose dissociation constant = 12.5 mM) as the mammalian enzyme. Little inhibition (less than 25%) was observed at normal glucose concentrations (1-5 mM), while significant inhibition (60-95%) occurred at glucose concentrations (50-500 mM) present in freezing-exposed animals. These results favour the hypothesis that in the normal state glucose regulates phosphorylase activity primarily through the promotion of dephosphorylation of phosphorylase a, whereas during freezing regulation is achieved through phosphorylase a inactivation. The caffeine dissociation constant (0.93 mM) and the degree of synergism between caffeine and glucose (interaction factor, alpha = 0.14) were also similar to that observed for the mammalian enzyme. Hence, if a caffeine-like ligand exists in vivo, it must be in low enough amounts during freezing to allow sufficient phosphorylase a activity for high glucose production.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0829-8211
pubmed:author
pubmed:issnType
Print
pubmed:volume
69
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
251-5
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
Glucose and caffeine regulation of liver glycogen phosphorylase activity in the freeze-tolerant wood frog Rana sylvatica.
pubmed:affiliation
Department of Biology, York University, Ont., Canada.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't