Figure 6.

Proposed ascorbic acid biosynthesis pathway of the Achatina fulica snail with collagen protein biosynthesis and modification. The synthesised ascorbic acid is transported into the endoplasmic reticulum and facilitates the hydroxylation of the procollagen precursor before being glycosylated to form tropocollagen and later released to the extracellular side for further modification and crosslinking (grey arrows). The ascorbic acid transport is driven by sodium-dependent vitamin C transporters or SVCTs (pink circles and pink arrows) and glucose transporters or GLUTs (blue circles and a blue arrow) for dehydroascorbic acid. DHAR and AO control interconversion between the dehydroascorbic acid and ascorbic acid (orange arrows).