Given the task definition and input, reply with output. In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.

 Acyl - coenzyme A : cholesterol acyltransferase ( ACAT ) is an intracellular enzyme involved in cellular cholesterol homeostasis and in atherosclerotic foam cell formation .

intracellular enzyme