6.
Structure-based topographical model of a hypothetical split path of chlorophyll breakdown in the peels of bananas. Chlorophylls are degraded by chloroplast enzymes to epi-pFCC (and possibly to the sFCC, 82-OH-epi-pFCC). Epi-pFCC (and/or 82-OH-epi-pFCC) are transported via the envelope into the cytosol (with assistance of a "catabolite" transporter, cat-tr). In the cytosol, 82-OH-epi-pFCC is converted to elusive modified FCCs (mFCCs), which are transported by a tonoplast-bound ABC-transporter (ABC-tr) into the vacuole. There, mFCCs isomerize to the Mc-NCCs. Alternatively, a hypothetical cytosolic enzymatic esterification converts 82-OH-epi-pFCC into Mc-FCC-56; subsequently, Mc-FCC-56 is likely to be converted to Mc-FCC-49 by the action of a β-glucosylating enzyme.