What is the first step in the enzymatic measurement of serum triglycerides using common methods?

• A. Hydrolysis of triglyceride by lipase to glycerol and fatty acids
• B. Oxidation of glycerol
• C. Transesterification to glycerol esters
• D. Direct measurement of triglyceride without hydrolysis

Answer: (A)

The starting step in these enzymatic triglyceride assays is lipase-catalyzed hydrolysis of the triglyceride into glycerol and free fatty acids. This is essential because the subsequent enzymatic chain is designed to detect glycerol, not the intact triglyceride. Once glycerol is released, it is phosphorylated by glycerol kinase to glycerol-3-phosphate, then oxidized by glycerol-3-phosphate oxidase to produce hydrogen peroxide, which drives a colorimetric or another detectable signal that correlates with triglyceride concentration. If you skipped hydrolysis, there would be no glycerol to measure, so the assay wouldn’t produce a meaningful signal. Transesterification to glycerol esters isn’t part of the standard enzymatic method, and direct measurement of triglyceride without hydrolysis isn’t compatible with how these assays generate a detectable readout.