Complex sentence: It is caused by a hereditary deficiency of the enzyme glucocerebrosidase (also known as acid β-glucosidase), leading to an accumulation of its substrate, the fatty substance glucocerebroside (also known as glucosylceramide).
Split into simpler sentences: It is caused by a hereditary deficiency of the enzyme glucocerebrosidase (also known as acid β-glucosidase). The enzyme acts on a fatty substance glucocerebroside (also known as glucosylceramide).