Methylated amino acids and lysosomal function in cultured heart cells

Methylated amino acids inhibit lysosomal function in cultured rat heart myocytes more effectively than the classically employed lysosomotropic weak bases. Moreover, L-leucine methyl ester (L-Leu-OMe) or L-methionine methyl ester (L-Meth-OMe) do not alter lysosomal pH or inactivate lysosomal cysteine proteinases, but do inhibit protein degradation more efficiently than either chloroquine or NH4Cl. These observations suggest that amino acid methyl esters are more effective probes to investigate lysosomal function in cultured myocytes than chloroquine or NH4Cl.