The role of kallikreins in growth factor processing: the kallikrein gene family from the African rodent Mastomys.

1. Kallikreins are trypsin-like serine proteases which have been implicated in the biosynthesis of a number of growth factors and hormones. Mastomys, an African rodent, is the only mammal other than mouse known to contain high levels of kallikreins and growth factors in its submandibular gland. Mastomys has a large kallikrein family similar to mouse and rat. Cloning and sequencing of several of these cDNAs demonstrates a high degree of homology with mouse and rat kallikreins, but careful analysis suggests that it will not be possible to determine the function of these kallikreins by sequence information alone. 2. It is not known whether a Mastomys kallikrein processes and binds to nerve growth factor (NGF) as in mouse submandibular gland. Mastomys NGF is bound to a protein similar in size, charge, and lack of esterase activity to alpha-NGF, a mouse kallikrein. However, the Mastomys NGF complex does not contain a proteolytically active kallikrein as does the mouse NGF complex. Thus, the identification of kallikreins as growth factor processing enzymes and the presence of a kallikrein family member in high-molecular-weight complexes in species other than mouse is still in question.