Laktózszintáz

Laktózszintáz, also known as lactose synthase, is an enzyme that plays a crucial role in the synthesis of lactose, the primary sugar found in milk. This enzyme is a heterodimer, meaning it is composed of two different protein subunits. The catalytic activity of laktózszintáz is provided by the alpha-lactalbumin subunit, which is specifically expressed in mammary glands during lactation. The other subunit is N-acetylglucosaminyltransferase I, a more ubiquitously expressed enzyme involved in glycoprotein synthesis.

The primary function of laktózszintáz is to catalyze the transfer of a galactose moiety from uridine diphosphate galactose (UDP-galactose) to glucose, forming lactose. The reaction can be summarized as: UDP-galactose + Glucose → Lactose + UDP. Alpha-lactalbumin modifies the substrate specificity of the N-acetylglucosaminyltransferase I subunit, promoting the binding of glucose over N-acetylglucosamine. This modification is essential for efficient lactose synthesis.

The synthesis of lactose by laktózszintáz is a critical process for providing energy and nutrients to nursing infants. The regulation of alpha-lactalbumin expression is tightly controlled by hormones, ensuring that lactose production occurs only when needed. Defects in laktózszintáz activity can lead to reduced lactose production, which may have implications for infant nutrition. Research into laktózszintáz has provided valuable insights into enzyme regulation and the biochemical pathways involved in milk production.