Catalyzes the attachment of leucine to its cognate tRNA. ATP + L-leucine + tRNA(Leu) = AMP + diphosphate + L-leucyl-tRNA(Leu) Ubiquitously expressed, but highest expression in tissues with high metabolic rates, such as skeletal muscle, heart, and kidney. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. Belongs to the class-I aminoacyl-tRNA synthetase family. Extended N-terminus.