Starvation and feeding with a high-carbohydrate diet induce changes in the specific activity of rat hepatic pyruvate kinase.

A highly specific radiosandwich assay for hepatic type-L pyruvate kinase (PK) determinants was developed. This assay was used to evaluate changes in PK specific activity which occur on starvation or feeding with a high-carbohydrate diet. Despite a large increase in both catalytic activity and immunoreactive protein, the calculated specific activity falls on feeding, and the opposite effect occurs on starvation. These change can be attributed to disproportionate changes in immunoreactive protein compared with changes in catalytic activity.