Production and characterization of recombinant guamerin, an elastase-specific inhibitor, in the methylotrophic yeast Pichia pastoris

The crystal structure of guamerin in complex with chymotrypsin and the development of an elastase-specific inhibitor

Guamerin, a canonical serine protease inhibitor from Hirudo nipponia, was identified as an elastase-specific inhibitor and has potential application in various diseases caused by elevated elastase concentration. However, the application of guamerin is limited because it also shows inhibitory activity against other proteases. To improve the selectivity of guamerin as an elastase inhibitor, it is essential to understand the binding mode of the inhibitor to elastase and to other proteases. For this purpose, we determined the crystal structure of guamerin in complex with chymotrypsin at 2.5 A resolution. The binding mode of guamerin on elastase was explored from the model structure of guamerin/elastase. Guamerin binds to the hydrophobic pocket of the protease in a substrate-like manner using its binding loop. In order to improve the binding selectivity of guamerin to elastase, several residues in the binding loop were mutated and the inhibitory activities of the mutants against elastase and chymotrypsin were monitored. The substitution of the Met36 residue for Ala in the P1 site increased the inhibitory activity against elastase up to 14-fold, while the same mutant showed 7-fold decreased activity against chymotrypsin compared to the wild-type guamerin. Furthermore, the M36A guamerin mutant more effectively protected endothelial cells against cell damage caused by elastase than the wild-type guamerin.

Production, purification and characterisation of recombinant Fahsin, a novel antistasin-type proteinase inhibitor

Serine proteinases from inflammatory cells, including polymorphonuclear neutrophils, are involved in various inflammatory disorders, like pulmonary emphysema and rheumatoid arthritis. Inhibitors of these serine proteinases are potential drug candidates for the treatment of these disorders, since they prevent the unrestricted proteolysis. This study describes a novel specific antistasin-type inhibitor of neutrophil serine proteinases, we called Fahsin. This inhibitor was purified from the Nile leech Limnatis nilotica, sequenced and heterologously expressed using a synthetic gene in the methylotrophic yeast Pichia pastoris, yielding 0.5 g(-l) of the protein in the culture medium. Recombinant Fahsin was purified to homogeneity and characterised by N-terminal amino acid sequencing and mass spectrometry. Inhibition-kinetic analysis showed that recombinant Fahsin is a fast, tight-binding inhibitor of human neutrophil elastase with inhibition constant in the nanomolar range. Furthermore, recombinant Fahsin was, in contrast to various other neutrophil elastase inhibitors, insensitive to chemical oxidation and biological oxidation via myeloperoxidase-generated free oxygen radicals. Thus, Fahsin constitutes a novel member of a still expanding family of naturally occurring inhibitors of serine proteinases with potential therapeutic use for treatment of human diseases.

Extended operation of a pressurized 75-L bioreactor for shLkn-1 production by Pichia pastoris using dissolved oxygen profile control

In this study, a dissolved oxygen (DO)-stat fed-batch process was conducted in a pressurized 75-L bioreactor, resulting in the production of the short version of human leukotactin-1 (shLkn-1) using Pichia pastoris as the host, with control of the DO-stat profile and an extension of the recombinant shLkn-1 production phase. By regulation of the exhaust-gas valve, we were able to maintain the vessel pressure at up to 120 kPa, in order to overcome DO limitations associated with the use of the DO-stat. The lowest DO value was adjusted by varying the feed pump speed, allowing us to control the DO-stat profile. This principle was successfully applied to both glycerol feeding during the growth phase and methanol feeding for the induction of shLkn-1. The extension of the methanol induction phase to a total of 192 h of culture time resulted in a shLkn-1 concentration of 2.5 g/L, and a total of 102 g of cumulative production. During this extended induction period, the C-terminal residue of shLkn-1 was truncated and this was confirmed by both reverse-phase HPLC and mass spectrometry.

Functional Screening of Serine Protease Inhibitors in the Medical Leech Hirudo medicinalis Monitored by Intensity Fading MALDI-TOF MS

The blood-feeding invertebrates are a rich biological source of drugs and lead compounds to treat cardiovascular diseases because they have evolved highly efficient mechanisms to feed on their hosts by blocking blood coagulation. In this work, we focused our attention on the leech Hirudo medicinalis. We performed, by "intensity fading" MALDI-TOF mass spectrometry, a comprehensive detection and functional analysis of pre-existent peptides and small proteins with the capability of binding to trypsin-like proteases related to blood coagulation. Combining "intensity fading MS" and off-line LC prefractionation allowed us to detect more than 75 molecules present in the leech extract that interact specifically with a trypsin-like protease over a sample profile of nearly 2,000 different peptides/proteins in the 2-20-kDa range. Moreover we resolved 232 individual components from the complex mixture, 13 of which have high sequence homology with previously described serine protease inhibitors. Our findings indicate that such extracts are much more complex than expected. Additionally, intensity fading MS, when complemented with LC separation strategies, seems to be a useful tool to investigate complex biological samples, establishing a new bridge between profiling, functional peptidomics, and subsequent drug discovery.

Human apolipoprotein(a) kringle V inhibits angiogenesis in vitro and in vivo by interfering with the activation of focal adhesion kinases

Apolipoprotein(a) [apo(a)] contains the largest numbers of kringle domains identified to date. Of these, apo(a) kringle V shows significant sequence homology with plasminogen kringle 5, which is reported to be a potent angiogenesis inhibitor. To determine the effects of apo(a) kringle V on angiogenesis, it was expressed as a soluble protein (termed rhLK8) in Pichia pastoris and its in vitro and in vivo anti-angiogenic properties were examined. rhLK8 inhibited the migration of human umbilical vein endothelial cells in vitro in a dose-dependent manner. This function was associated with the down-regulation of the activation of focal adhesion kinase and the inhibition of the consequent formation of actin stress fibers/focal adhesions. rhLK8 also inhibited new capillary formation in vivo, as assessed by the chick chorioallantoic membrane assay and the Matrigel plug assay. These results indicate that rhLK8 may be an effective angiogenesis inhibitor both in vitro and in vivo.