Human Intestinal-Type Alkaline Phosphatase / IAP (ALPI) Protein

Background

Intestinal-type alkaline phosphatase (ALPI) is a glycoprotein enzyme primarily expressed on the luminal surface of intestinal epithelial cells, particularly in the small intestine. It plays a crucial role in maintaining gut homeostasis by detoxifying lipopolysaccharides (LPS), dephosphorylating inflammatory mediators, and promoting a healthy microbiota. ALPI is also involved in nutrient absorption, such as the hydrolysis of dietary phosphate esters, contributing to the regulation of phosphate metabolism. Its expression is upregulated in response to inflammation and microbial imbalance, acting as a protective mechanism against intestinal permeability and systemic endotoxemia. Additionally, ALPI prevents excessive immune activation by neutralizing pro-inflammatory signals, which is essential for preventing conditions such as inflammatory bowel disease (IBD) and sepsis. Alterations in ALPI expression or activity have been linked to gastrointestinal disorders, including Crohn's disease and ulcerative colitis. Its multifunctional role highlights its importance in gut health, immune modulation, and overall metabolic regulation.