Catalyzes a carbon-carbon cleavage reaction; cleaves a 2-hydroxy-3-methylacyl-CoA into formyl-CoA and a 2-methyl-branched fatty aldehyde. Binds 1 Mg(2+) ion per subunit. Binds 1 thiamine pyrophosphate per subunit. Peroxisomal targeting signal 1 (PTS1) is a tripeptide located at the C-terminus of more than 95% of all peroxisomal matrix proteins. The prototypical PTS1 is the terminal tripeptide SKL (serine-lysine-leucine) but the consensus of PTS1 is defined as [S/A/H/C/E/P/Q/V] [K/R/H/Q] [L/F]. However, this description of the PTS1 consensus must probably be expanded beyond the terminal tripeptide. Does not affect growth on oleate. Belongs to the TPP enzyme family.