Quantitative Proteomics Analysis by Sequential Window Acquisition of All Theoretical Mass Spectra-Mass Spectrometry Reveals Inhibition Mechanism of Pigments and Citrinin Production of Monascus Response to High Ammonium Chloride Concentration

Various Monascus bioactive metabolites used as food or food additives in Asia for centuries are subjected to constant physical and chemical changes and different Monascus genus. With the aim to identify enzymes that participate in or indirectly regulate the pigments and citrinin biosynthesis pathways of Monascus purpureus cultured under high ammonium chloride, the changes of the proteome profile were examined using sequential window acquisition of all theoretical mass spectra-mass spectrometry-based quantitative proteomics approach in combination with bioinformatics analysis. A total of 292 proteins were confidently detected and quantified in each sample, including 163 that increased and 129 that decreased (t-tests, p <= 0.05). Pathway analysis indicated that high ammonium chloride in the present study accelerates the carbon substrate utilization and promotes the activity of key enzymes in glycolysis and beta-oxidation of fatty acid catabolism to generate sufficient acetyl-CoA. However, the synthesis of the monascus pigments and citrinin was not enhanced because of inhibition of the polyketide synthase activity. All results demonstrated that the cause of initiation of pigments and citrinin synthesis is mainly due to the apparent inhibition of acyl and acetyl transfer by some acyltransferase and acetyltransferase, likely malony-CoA:ACP transacylase.