Component of the tagatose-1,6-bisphosphate aldolase KbaYZ that is required for full activity and stability of the Y subunit. Could have a chaperone-like function for the proper and stable folding of KbaY. When expressed alone, KbaZ does not show any aldolase activity. Carbohydrate metabolism; D-tagatose 6-phosphate degradation; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-tagatose 6-phosphate: step 2/2. Forms a complex with KbaY. Belongs to the GatZ/KbaZ family. KbaZ subfamily.