Lithostathine, an inhibitor of CaCO3 crystal growth in pancreatic juice, induces bacterial aggregation.

Lithostathine is a pancreatic secretory protein which controls CaCO3 crystal growth in pancreatic juice. Trypsin hydrolysis of the molecule generates two fragments of 11 and 133 amino acids. The N-terminal undecapeptide bears the inhibitory activity for crystal growth. We demonstrate that the C-terminal part of the molecule, which is structurally related to Ca(2+)-dependent lectins, can induce bacterial aggregation. Ca(2+)- and pH-dependent aggregation was obtained for Escherichia coli strain KH 802 and 9 of 19 strains isolated from the predominant flora of human feces. Aggregation of E. coli could be reversed by dilution and bacteria could resume normal growth. Lithostathine is apparently the only component of normal pancreatic juice displaying such activity. Lithostathine is therefore a bifunctional protein which might be involved in the control of the bacterial ecosystem in the intestine.