Heavy (HMM) and light (LMM) meromyosin chains are found in

The heavy and light meromyosin chain are components of muscle myosin filament. Each myosin (thick) filament is a polymerised protein with Meromyosin as monomeric proteins.
Each meromyosin has two parts:

• Heavy meromyosin (HMM) - Globularhead with a short arm. It projects outwards at regular intervals and angle from the surface of a polymerised myosin filament and is known as cross arm. The globular head is an active ATPase enzyme which has binding sites for ATP and active sites for actin.
• Light meromyosin (LMM) - Tail