SFTPD and chronic obstructive pulmonary disease: Both codons are read by the same tRNAGCUSer; however, in pulmonary tissues, the AGU codon is translated with 2-fold higher velocity (61, 62), suggesting that this subtle decrease of the decoding rate of the Ser AGT codon may over longer periods of time cumulatively affect the folding and surfactant protein-D levels in COPD patients.