Effect of short-chain aldehydes on the enzymatic activity of pyruvate kinase

The oxidative modification of lipids containing polyunsaturated fatty acids results in a great diversity of reactive products including short-chain aldehydes, which can covalently modify proteins. The cellular effects of some of these oxidative post-translational modifications are yet to be understood, so there is a need to study the effect of small reactive aldehydes on the activity of enzymes. The model proteins lysozyme and human serum albumin were used to map aldehyde modifications by mass spectrometry (MS). The same approach was used to treat pyruvate kinase (PK), an enzyme that catalyses the last step in glycolysis and regulates tumour growth. PK was treated for 10 mins with varying concentrations of acrolein, malondialdehyde and 4-hydroxy-2-hexenal, before assaying the enzymatic activity. In each case, a dose-dependent effect on the activity was observed. Additionally, analysis of tryptic digests of modified PK by LC-MS/MS allowed these modifications to be identified and located. Inhibition of PK has been found to be associated with cancer progression, and this study suggests that reactive short-chain aldehydes could contribute to this and influence cell survival, as well as providing novel information on the structure-function relationship of lipoxidation.