What is the Origin of Hormone-Sensitive Lipase?

The name is purely descriptive, reflecting the enzyme's primary function—a lipase that is highly sensitive to hormonal regulation. Its discovery elucidated a key regulatory step in fat metabolism. HSL's function is a classic example of endocrine control over metabolic processes, as its activity is directly phosphorylated and activated by catecholamines and suppressed by insulin.

What is the Mechanism of Hormone-Sensitive Lipase?

HSL is primarily activated through phosphorylation by protein kinase A (PKA), which is itself activated by elevated cyclic AMP (cAMP) levels resulting from the binding of lipolytic hormones, such as epinephrine and glucagon, to their cell surface receptors. Conversely, insulin, a major anabolic hormone, dephosphorylates and inhibits HSL activity through phosphodiesterase and protein phosphatase pathways. This reciprocal regulation ensures that fat is mobilized when energy is needed and stored when energy is abundant.

Hormone-Sensitive Lipase

Meaning

Hormone-Sensitive Lipase (HSL) is a cytosolic enzyme predominantly expressed in adipose tissue that catalyzes the hydrolysis of stored triglycerides into free fatty acids and glycerol, a process known as lipolysis. This enzyme’s activity is highly regulated by various hormonal signals, making it a central mediator in the body’s energy mobilization and utilization pathways. It is crucial for providing energy substrates during periods of fasting or increased metabolic demand.