Abstract Summary: The searchable mutant database PLPMDB has been developed to provide rapid and simple access to relevant mutant information on pyridoxal-5′-phosphate dependent enzymes. All data have been extracted from publications and publicly available databases, then organized in a relational database to enable searching via a web-based search form. The current version of PLPMDB contains 688 mutants described in 220 research papers. The database is a useful tool for planning mutant experiments and for interpretation of information from such experiments. Availability: PLPMDB is freely accessible from http://www.studiofmp.com/plpmdb/index.htm