The Potential Roles of Transacylation in Intracellular Lipolysis and Related Qssa Approximations

Area of Science:

• Biochemistry
• Cell Biology
• Metabolic Regulation

Background:

• Fatty acids (FAs) are essential energy sources and signaling molecules.
• Adipose triglyceride lipase (ATGL) is key in releasing FAs from stored triacylglycerols (TGs).
• ATGL also catalyzes diacylglycerol (DG) transacylation, but its physiological relevance is unclear.

Purpose of the Study:

• To investigate the physiological relevance of ATGL-mediated diacylglycerol (DG) transacylation.
• To determine if DG transacylation is a byproduct or a functional aspect of ATGL activity.

Main Methods:

• Extensive asymptotic analysis of ATGL kinetics.
• Quasi-steady-state approximations (QSSA) with higher-order corrections.
• Numerical simulations to model ATGL activity.
• Parameter sensitivity analysis for QSSA validation.

Main Results:

• Transacylation can significantly alter downstream product levels (up to 80% increase or 30% decrease).
• The impact of transacylation depends on kinetic parameters and the state of the hydrolytic machinery.
• QSSA validity assessment should include parameter sensitivity derivatives.

Conclusions:

• ATGL-mediated DG transacylation is biologically relevant.
• Transacylation provides feedback mechanisms and stability to the lipolytic process in adipocytes.