Pyruvate dehydrogenase kinase (PDHK) is a group of enzymes that regulate the activity of the pyruvate dehydrogenase complex (PDH complex), consisting of four subtypes (PDHK1-4), located in the mitochondria. It phosphorylates the E1 subunit of pyruvate dehydrogenase, inhibiting its activity and thereby regulating the rate at which glycolytic products enter the tricarboxylic acid cycle. PDHK is expressed in various tissues, and its activity is regulated by multiple factors, including nutritional status and hormone levels. Specific gene expression and mutations can affect the risk of metabolic diseases such as diabetes.