The cDNA for the trypsin-like serine protease gene (TLSP, HGMW-approved symbol 
PRSS20) has been recently identified. TLSP is expressed in brain and skin 
tissues but little else is known about this new serine protease gene. In this 
paper, we describe the complete genomic organization and precise mapping of the 
TLSP gene. This gene spans 5.3 kb of genomic sequence on chromosome 19q13.3-q13. 
4. The gene consists of six exons, the first of which is untranslated. All 
splice junctions follow the GT/AG rule, and the intron phases are identical to 
those of other kallikrein-like genes, including zyme (PRSS9), NES1 (PRSSL1), and 
neuropsin (PRSS19). Fine-mapping of the area indicates that TLSP lies downstream 
from the PSA, zyme, neuropsin, and NES1 genes. Significant sequence homologies 
were found between TLSP and other human kallikreins. Furthermore, there is 
conservation of the catalytic triad (histidine, aspartic acid, serine) and of 
the number of coding exons (five; the same in all members of the kallikrein gene 
family). We thus suggest that TLSP is a new member of the human kallikrein gene 
family. TLSP is expressed in many tissues including cerebellum, prostate, 
salivary glands, stomach, lung, thymus, small intestine, spleen, liver, and 
uterus. TLSP expression appears to be regulated by steroid hormones in the 
breast carcinoma cell line BT-474.