Component of the phosphopantothenoylcysteine decarboxylase (PPCDC) involved in the coenzyme A synthesis. Acts as an inhibitory subunit of protein phosphatase PPZ1, which is involved in many cellular processes such as G1-S transition or salt tolerance. Interacts with the C-terminal domain of PPZ1. Component of the phosphopantothenoylcysteine decarboxylase (PPCDC) complex, a heterotrimer composed of CAB3, SIS2 and VHS3. Belongs to the HFCD (homooligomeric flavin containing Cys decarboxylase) superfamily.