Give me A5 for lipoprotein hydrolysis!
J. Clin. Invest. Martin Merkel, et al. 115:2694 doi:10.1172/JCI26712 [Go to this article.]

Figure 1
Triglyceride-lowering effect of APOA5. (A) Triglyceride-rich lipoproteins such as VLDL are hydrolyzed by the lipolytic action of dimeric LPL, which is bound to heparan sulfate proteoglycans on the vascular endothelium. We propose that APOA5 targets VLDL to proteoglycans, placing VLDL in close proximity to LPL. At the same time, APOA5 may activate proteoglycan-bound LPL by stabilizing the dimerized conformation or by binding to an LPL allosteric site. After hydrolysis, remnant particles (Rem) are released into the circulation, and APOA5 can be transferred and reused by other VLDL particles. In the postprandial situation, HDL can act as an APOA5 donor for intestinally derived chylomicrons. Thus, APOA5 is a potent activator of the natural lipolytic system. (B) Proposed situation in patients with the Q139X mutation in APOA5 (Q139X-APOA5). Truncated APOA5 is not associated with lipoproteins and cannot sufficiently target triglyceride-rich lipoproteins to proteoglycans. Instead, binding of the Q139X mutation in APOA5 to proteoglycan-bound LPL results in detachment and degradation of LPL.