A low-Mr lipase activation factor cooperating with lipase modulator protein LimL in Pseudomonas sp. strain 109.

Pseudomonas sp. strain 109 produces a unique lipase (LipL) which efficiently catalyses intramolecular transesterification of omega-hydroxyesters to form macrocyclic lactones. In vivo production of enzymically active LipL requires lipase modulator protein (LimL), which functions as a molecular chaperone for the correct folding of LipL. However, previous work has shown that LipL forms a tight complex with LimL in vitro and the resulting LipL-LimL complex is only partially active, suggesting an additional mechanism that facilitates the dissociation of the complex to form enzymically active LipL. In the present work, a low-Mr compound (lipase activation factor, LAF) was found in Pseudomonas sp. strain 109 that when added to the LipL-LimL complex resulted in the activation of LipL. Ca2+ ions also enhanced lipase activity, but the instantaneous activation by Ca2+ was different from the gradual and time-dependent activation by LAF, indicating the novel nature of this compound. LAF passed through an ultrafiltration membrane with an Mr cut-off of 3000 and showed an apparent Mr of 330+/-30 on Superdex Peptide gel-filtration chromatography. Treatment of the LipL-LimL complex with LAF liberated free active LipL, indicating that LAF was necessary to dissociate the LipL-LimL complex.