Parvulins and FKBPs are members of the peptidyl-prolyl cis/trans isomerases (PPIase) enzyme family whose role is to catalyze the interconversion between the cis trans forms of a peptide bond preceding internal proline residues in a polypeptide substrate. Members of the parvulin subfamily have been found to be involved in a variety of diseases, including Alzheimer's disease and cancer and are also considered possible antiparasitic targets. Genes Y110A2AL.13 (pin-1) and Y48C3A.16 (pin-4) were found in the worm's genome, possibly encoding parvulins. One is homologous to human and fly PIN whereas the other is homologous to human and fly PIN4. Both were expressed in Escherichia coil, purified and found to have in vitro PPIase activity. Expression levels of both genes, as well as the fkb genes (that encode FK506-binding proteins) were measured during development and under cold or heat stress conditions. The results revealed a potential role for these genes under temperature-related stress. RNAi silencing was performed for wild type and mutant strain worms under normal and cold or heat stress conditions. A reduced life-span was observed when pin-4 dsRNA was fed to the fkb-5 deficient worms. Our work presents a first attempt to characterize the Caenorhabditis elegans parvulins and may present an interesting starting point for further experimentation concerning their role, along with the FKBP subfamily, in nematode physiology and their possible use as antiparasitic targets. (C) 2012 Elsevier Inc. All rights reserved.