On the basis of peptide sequences, several research amount of leucine incorporated per CUG codon was not quantitatively determined, it is clear that the incorporation groups have reported that codon CUG corresponds only to serine in C.maltosa (Sugiyama et al., 1995) and was mediated by the leucyl-tRNA Ser CAG. We thus concluded that codon CUG was simultaneously assigned to C.albicans (Santos and Tuite, 1995a; White et al., 1995) . No leucine-inserted peptide was detected in these studies. serine and leucine in the normal translation process in C.maltosa. A quantitative analysis of the amino acids However, we consider that any peptide with a leucine which was inserted for the codon CUG might have been attached to the tRNA indicated that 3% of tRNA Ser CAG is leucylated in C.zeylanoides cells. Such a high level of missed during purification or was undetectable in the peptide sequencing, because the amount of leucine-inserted leucylation is far beyond conventional misacylation, whose rate is estimated to be less than 10 -4 . Unless a proofreading peptide (~3%) would have been too low to be positively identified in sequencing experiments. mechanism exists on the ribosome, incorporation of leucine at CUG codon sites may reflect the relative ratio of