Microsomal ethanol oxidizing system: transcriptional and posttranscriptional regulation of cytochrome P450, CYP2E1.

CYP2E1 is solely responsible for microsomal P450-mediated ethanol oxidation activity. This enzyme is also involved in a pathway leading to gluconeogenesis from ketone bodies and in metabolic activation of numerous foreign compounds to intermediates that can be toxic to cells. Metabolic activation of certain procarcinogens by CYP2E1 may also lead to cell transformation. Regulation of CYP2E1 is especially intriguing. The CYP2E1 gene is transcriptionally activated in rat liver from a dormant state within a few hours after birth. This activation is due in part to the participation of a transcription factor designated hepatocyte nuclear factor 1 or HNF-1. In adult animals, constitutive expression of the enzyme is controlled to some degree by growth hormone. CYP2E1 is also regulated by many of its substrates through a substrate-induced stabilization of the enzyme. Under extreme conditions of fasting and uncontrolled diabetes CYP2E1 mRNA is stabilized.