The disclosure is directed to a method of engineering a heterologous thioesterase (TE) enzyme to interact with endogenous acyl-ACP proteins in order to produce molecules of interest in a bacterial host. The method can identify amino acids at the binding interface between the heterologous TE and the endogenous acyl-ACP that can be substituted so that the heterologous TE can better interact with the endogenous acyl-ACP. Mutant heterologous TE enzymes with improved interactions with the endogenous acyl-ACP are also provided.