Identification of an Acidic Amino Acid Permease Involved in d-Aspartate Uptake in the Yeast Cryptococcus humicola

d-aspartate oxidase (DDO) catalyzes the oxidative deamination of acidic d-amino acids, and its production is induced by d-Asp in several eukaryotes. The yeast Cryptococcus humicola strain UJ1 produces large amounts of DDO (ChDDO) only in the presence of d-Asp. In this study, we analyzed the relationship between d-Asp uptake by an amino acid permease (Aap) and the inducible expression of ChDDO. We identified two acidic Aap homologs, named “ChAap4 and ChAap5,” in the yeast genome sequence. ChAAP4 deletion resulted in partial growth defects on d-Asp as well as l-Asp, l-Glu, and l-Phe at pH 7, whereas ChAAP5 deletion caused partial growth defects on l-Phe and l-Lys, suggesting that ChAap4 might participate in d-Asp uptake as an acidic Aap. Interestingly, the growth of the Chaap4 strain on d- or l-Asp was completely abolished at pH 10, suggesting that ChAap4 is the only Aap responsible for d- and l-Asp uptake under high alkaline conditions. In addition, ChAAP4 deletion significantly decreased the induction of DDO activity and ChDDO transcription in the presence of d-Asp. This study revealed that d-Asp uptake by ChAap4 might be involved in the induction of ChDDO expression by d-Asp.

The Role of an Acidic Peptide in Controlling the Oxidation Process of Walnut Oil

Here, the mechanism of action of an antioxidant peptide rich in acidic amino acid residues in controlling lipid oxidation is discussed. Firstly, in the presence of this peptide, the fluorescence intensity of lipid peroxide in samples of walnut oil was very low, indicating that the peptide prevented the formation of lipid peroxides. Secondly, the production of lipid-derived radicals of oil was reduced by 23% following addition of the anti-oxidative peptide. Thirdly, Raman shifts of the lipid with the anti-oxidative peptide showed that acidic amino acid residues of the peptide were involved in delaying lipid oxidation. Finally, seven peptide inhibitors were synthesized with variations to the amino acid sequence of the original peptide, and Glu–Asp was proven to enhance the peptide’s superoxide anion radical scavenging activity and decrease the formation of linoleic acid peroxides. Our findings emphasize the potential value of acidic amino acid residues in protecting unsaturated fatty acids from oxidation.

Surface charge engineering of nanosized CuS via acidic amino acid modification enables high peroxidase-mimicking activity at neutral pH for one-pot detection of glucose

Surface charge engineering of nanosized CuS via acidic amino acid (Asp) modification enables unprecedented peroxidase-mimicking activity at neutral pH.