Carnitine O-palmitoyltransferase 1, muscle isoform is a protein that in humans is encoded by CPT1B, is one isoform of carnitine palmitoyltransferase I (CPT1). This protein is produced by a bicistronic gene which also produces the CHKB protein from a non-overlapping reading frame, and acts as an emzyme that catalyzed the following reaction: This protein is produced by a bicistronic gene which also produces the CHKB protein from a non-overlapping reading frame.