Kallikreins belong to a family of serine proteases that are widespread 
throughout living organisms, expressed in diverse tissue-specific patterns, and 
known to have highly diverse physiological functions. The 15 human and 24 mouse 
kallikreins have been implicated in pathophysiology of brain, kidney, and 
respiratory and reproductive systems and often are used as cancer biomarkers. To 
better elucidate the structure and evolutionary origin of this important gene 
family in the pig, we have constructed a contiguous BAC clone-derived physical 
map of the porcine kallikrein gene region and have fully sequenced a BAC clone 
containing 13 kallikrein genes, 11 of which are novel. Radiation hybrid mapping 
assigns this kallikrein-gene-rich region to porcine chromosome 6. Phylogenetic 
and percent identity plot-based analyses revealed strong structure and order 
conservation of kallikreins among four mammalian species. Reverse 
transcriptase-polymerase chain reaction-based expression analysis of porcine 
kallikreins showed a complex expression pattern across different tissues with 
the thymus being the only tissue expressing all 13 kallikrein genes. [The 
sequence data described in this paper has been submitted to GenBank under 
Accession No. AC149292].