Table 1.

The lysosome is an essential energy generator.

Macromolecule	Defective gene/protein	S. cerevisiae	C. elegans	M. musculus	H. sapiens
Glycogen	GAA (glucosidase, α; acid)	Glycogen accumulation119	Protein conserved120 but phenotype not reported	Increased glycogen content in cardiac and skeletal muscle121	Pompe disease: general myopathy, cardiomyopathy, pulmonary failure122-124
Triglycerides and cholesteryl esters	LIPA (lipase A, lysosomal acid, cholesterol esterase)	Increased steryl ester content79	Increased fat mass77	Massive ectopic fat accumulation, shortened life span125	CESD and Wolman disease: massive ectopic fat accumulation, mild symptoms to infant death126

The essential, and consequently conserved, role of lysosomal hydrolases in providing energy units by processing energy-dense nutrients is illustrated here by the phenotypic effects of their mutation in eukaryotes ranging from yeast to humans. CESD, cholesteryl ester storage disease.