Chain-length factor (CLF) is a factor required for polyketide chain initiation of aromatic antibiotic-producing polyketide synthases (PKSs) of filamentous bacteria. CLFs have been shown to have decarboxylase activity towards malonyl-acyl carrier protein (ACP). CLFs are similar to other elongation ketosynthase domains, but their active site cysteine is replaced by a conserved glutamine.
Jiyao W et al.(2023). "The conserved domain database in 2023.",