The glandular kallikrein family is composed of structurally related serine 
proteases. Studies show that the mouse family encompasses at least 14 highly 
conserved functional genes, but of these only the tissue kallikarein has a human 
ortholog. In man, the tissue kallikrein display high sequence similarity with 
prostate specific antigen and human glandular kallikrein 2, suggesting that they 
evolved after the separation of primates and rodents. A phylogenetic study of 
the genes encoding glandular kallikreins in species evolutionarily located 
between rodents and man may reveal interesting details on how the gene family 
evolved, which in turn could yield information about the function of the 
proteins. Therefore, we have initiated a study of the glandular kallikreins of 
the cotton-top tamarin (Saguinus oedipus), a New World Monkey. Here, we report 
the cloning and nucleotide sequence of one of these, the tissue kallikrein gene. 
The gene of 4.4 kb is composed of five exons, and the structure is 90% similar 
to that of the orthologous human gene. It gives rise to a polypeptide of 261 
amino acids, including a signal peptide of 17 residues, a pro-piece of 7 
residues, and the mature protein of 237 residues with an estimated molecular 
mass of 26.3 kD. The similarity to the human prostate specific antigen and human 
glandular kallikrein 2 genes is 73% and 72%, respectively, including introns and 
flanking regions. The lower similarity to these genes compared with the human 
tissue kallikrein gene indicates that they, or a progenitor to them, arose in 
primates prior to the separation of New and Old World monkeys. Genomic Southern 
blots also show that the cotton-top tamarin genome encompasses at least one more 
glandular kallikrein gene.