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Tyrphostin 47 nonenzymatically decarboxylates [1-14C]-pyruvate
F L Kiechle1, D M Staudacher, J P Ofenstein
1Department of Clinical Pathology, William Beaumont Hospital, Royal Oak, MI 48073-6769.
Annals of Clinical and Laboratory Science
|September 1, 1994
Summary
Tyrphostins do not directly activate pyruvate dehydrogenase kinase. Tyrphostin 47 interferes with pyruvate assays, leading to inaccurate results regarding enzyme activity.
Area of Science:
- Biochemistry
- Enzymology
- Molecular Biology
Background:
- Tyrphostins are known inhibitors of tyrosine kinases.
- Pyruvate dehydrogenase kinase (PDK) is a serine/threonine kinase that inactivates pyruvate dehydrogenase (PDH).
- PDK represents a novel family of protein kinases.
Purpose of the Study:
- To investigate the effect of tyrphostins on pyruvate dehydrogenase kinase activity.
- To determine if tyrphostins modulate pyruvate dehydrogenase activity in rat adipocyte mitochondria.
Main Methods:
- Assessing pyruvate dehydrogenase kinase activity via [1-14C]-lactate oxidation.
- Measuring pyruvate dehydrogenase activity using [1-14C]-pyruvate as a substrate in isolated mitochondria.
- Testing tyrphostins 47 and 23 for their effects on enzyme activity.
Main Results:
- Tyrphostin 47 appeared to activate PDK in initial lactate oxidation assays.
- In subsequent assays, tyrphostin 47 showed a dose-dependent increase in PDH activity, while tyrphostin 23 did not.
- The observed increase in PDH activity was found to be due to non-enzymatic decarboxylation of [1-14C]-pyruvate by tyrphostin 47, not direct enzyme activation.
- Neither tyrphostin directly affected pyruvate dehydrogenase kinase activity.
Conclusions:
- Tyrphostins do not directly modulate pyruvate dehydrogenase kinase activity.
- Tyrphostin 47 causes analytical interference in pyruvate dehydrogenase assays utilizing [1-14C]-pyruvate.
- Care must be taken when interpreting results from assays involving [1-14C]-pyruvate and tyrphostin 47.