Activity of Plasmin and Streptokinase-Activator on Substituted Arginine and Lysine Esters

Development and Testing of Thrombolytics in Stroke

Despite recent advances in recanalization therapy, mechanical thrombectomy will never be a treatment for every ischemic stroke because access to mechanical thrombectomy is still limited in many countries. Moreover, many ischemic strokes are caused by occlusion of cerebral arteries that cannot be reached by intra-arterial catheters. Reperfusion using thrombolytic agents will therefore remain an important therapy for hyperacute ischemic stroke. However, thrombolytic drugs have shown limited efficacy and notable hemorrhagic complication rates, leaving room for improvement. A comprehensive understanding of basic and clinical research pipelines as well as the current status of thrombolytic therapy will help facilitate the development of new thrombolytics. Compared with alteplase, an ideal thrombolytic agent is expected to provide faster reperfusion in more patients; prevent re-occlusions; have higher fibrin specificity for selective activation of clot-bound plasminogen to decrease bleeding complications; be retained in the blood for a longer time to minimize dosage and allow administration as a single bolus; be more resistant to inhibitors; and be less antigenic for repetitive usage. Here, we review the currently available thrombolytics, strategies for the development of new clot-dissolving substances, and the assessment of thrombolytic efficacies in vitro and in vivo.

Units and Methods of Proteolytic Activity Determination

Background:

In order to organize and give a better understanding of the existing population of protease activity units together with their respective methods of enzymatic activity assessment, there is a need of their clear classification system.

Results and Conclusion:

The following system has been proposed: Enzyme Centered Units (ECU) equivalent to Enzyme Process Unit notation; Protein Centered Units (PCU) equivalent to Protein Process Unit notation; Legal Authority and Enzyme Centered Units (LAECU) equivalent to Enzyme Centered Units system additionally related to a legal authority or an organization. The suitable ways for the mutual conversion of commonly used units and their conversion into the standard SI units have been included. A convenient gravity/spectrophotometer test of proteolytic activity with the use of three protein types has also been proposed. The test gives high degree of confidence of the experimental determination for a wide spectrum of protease activity in samples of plant origin. The whole paper allows both theoretical and practical orientation in the range of different proteolytic activity units as well as in the methods of their determination.

Study of proteolysis in river buffalo mozzarella cheese using a proteomics approach

The guarantee of the origin and quality of raw material is essential for the protection and valorization of Campana buffalo mozzarella cheese. The risk of utilization of semifinished products and stored milk in substitution for fresh milk is increasing, due to the continuous desire to reduce production costs. A proteomics approach and electrophoresis survey of retail mozzarella cheeses indicated different rates of proteolysis in the production of dairy industries. The use of fresh milk and correct cheesemaking protocol yielded only γ-caseins, which are derived from β-casein by plasmin, and para-κ-casein, which is derived from κ-casein by chymosin. The detection of abnormal hydrolysis resulting in β- and αS1-casein fragments, identified by mass spectrometry, indicates the use of stored milk or stored and pressed curd, or the reuse of unsold mozzarella cheese, to produce mozzarella. The formation of γ-caseins and other fragments during a long storage of raw materials at room or refrigeration temperature was ascribed to plasmin (endogenous milk enzyme), whereas formation of αS1-casein fragments, mainly αS1-I(6P)- and αS1-I(7P)-casein during the storage of curd was ascribed to the action of chymosin (exogenous enzyme) from rennet. Sodium dodecyl sulfate-PAGE and alkaline urea-PAGE permitted us to evaluate the freshness of the raw materials used in the manufacturing of buffalo mozzarella cheese and to reveal possible inappropriate preservation.

A novel clot lysis assay for recombinant plasminogen activator

Recombinant plasminogen activator (r-PA, reteplase) is an engineered variant of alteplase. When expressed in E. coli, it appears as inclusion bodies that require refolding to recover its biological activity. An important step following refolding is to determine the activity of refolded protein. Current methods for enzymatic activity of thrombolytic drugs are costly and complex. Here a straightforward and low-cost clot lysis assay was developed. It quantitatively measures the activity of the commercial reteplase and is also capable of screening refolding conditions. As evidence for adequate accuracy and sensitivity of the current assay, r-PA activity measurements are shown to be comparable to those obtained from chromogenic substrate assay.

Activity assessment of microbial fibrinolytic enzymes

Conversion of fibrinogen to fibrin inside blood vessels results in thrombosis, leading to myocardial infarction and other cardiovascular diseases. In general, there are four therapy options: surgical operation, intake of antiplatelets, anticoagulants, or fibrinolytic enzymes. Microbial fibrinolytic enzymes have attracted much more attention than typical thrombolytic agents because of the expensive prices and the side effects of the latter. The fibrinolytic enzymes were successively discovered from different microorganisms, the most important among which is the genus Bacillus. Microbial fibrinolytic enzymes, especially those from food-grade microorganisms, have the potential to be developed as functional food additives and drugs to prevent or cure thrombosis and other related diseases. There are several assay methods for these enzymes; this may due to the insolubility of substrate, fibrin. Existing assay methods can be divided into three major groups. The first group consists of assay of fibrinolytic activity with natural proteins as substrates, e.g., fibrin plate methods. The second and third groups of assays are suitable for kinetic studies and are based on the determination of hydrolysis of synthetic peptide esters. This review will deal primarily with the microorganisms that have been reported in literature to produce fibrinolytic enzymes and the first review discussing the methods used to assay the fibrinolytic activity.