During the resorbable-polymer-boom of the 1970s and 1980s, polycaprolactone (PCL) was used in the biomaterials field and a number of drug-delivery devices. Its popularity was soon superseded by faster resorbable polymers which had fewer perceived disadvantages associated with long term degradation (up to 3-4 years) and intracellular resorption pathways; consequently, PCL was almost forgotten for most of two decades. Recently, a resurgence of interest has propelled PCL back into the biomaterials-arena. The superior rheological and viscoelastic properties over many of its aliphatic polyester counterparts renders PCL easy to manufacture and manipulate into a large range of implants and devices. Coupled with relatively inexpensive production routes and FDA approval, this provides a promising platform for the production of longer-term degradable implants which may be manipulated physically, chemically and biologically to possess tailorable degradation kinetics to suit a specific anatomical site. This review will discuss the application of PCL as a biomaterial over the last two decades focusing on the advantages which have propagated its return into the spotlight with a particular focus on medical devices, drug delivery and tissue engineering.

The return of a forgotten polymer : Polycaprolactone in the 21st century

Reactive aldehydes derived from reducing sugars and lipid peroxidation play a critical role in the formation of advanced glycation end (AGE) products and oxidative tissue damage. We have recently proposed another mechanism for aldehyde generation at sites of inflammation that involves myeloperoxidase, a heme enzyme secreted by activated phagocytes. We now demonstrate that human neutrophils employ the myeloperoxidase-H202-chloride system to produce alpha-hydroxy and alpha,beta-unsaturated aldehydes from hydroxy-amino acids in high yield. Identities of the aldehydes were established using mass spectrometry and high performance liquid chromatography. Activated neutrophils converted L-serine to glycolaldehyde, an alpha-hydroxyaldehyde which mediates protein cross-linking and formation of Nepsilon-(carboxymethyl)lysine, an AGE product. L-Threonine was similarly oxidized to 2-hydroxypropanal and its dehydration product, acrolein, an extremely reactive alpha,beta-unsaturated aldehyde which alkylates proteins and nucleic acids. Aldehyde generation required neutrophil activation and a free hydroxy-amino acid; it was inhibited by catalase and heme poisons, implicating H202 and myeloperoxidase in the cellular reaction. Aldehyde production by purified myeloperoxidase required H202 and chloride, and was mimicked by reagent hypochlorous acid (HOCl) in the absence of enzyme, suggesting that the reaction pathway involves a chlorinated intermediate. Collectively, these results indicate that the myeloperoxidase-H202-chloride system of phagocytes converts free hydroxy-amino acids into highly reactive alpha-hydroxy and alpha,beta-unsaturated aldehydes. The generation of glycolaldehyde, 2-hydroxypropanal, and acrolein by activated phagocytes may thus play a role in AGE product formation and tissue damage at sites of inflammation.

/pdf/human-neutrophils-employ-the-myeloperoxidase-hydrogen-4v2a60ix6s.pdf

Human neutrophils employ the myeloperoxidase-hydrogen peroxide-chloride system to convert hydroxy-amino acids into glycolaldehyde, 2-hydroxypropanal, and acrolein. A mechanism for the generation of highly reactive alpha-hydroxy and alpha,beta-unsaturated aldehydes by phagocytes at sites of inflammation.

Flavones: An important scaffold for medicinal chemistry

Purification strategies for microbial lipases

Lipases are important industrial enzymes. Most of the lipases operate at lipid-water interfaces enabled by a mobile lid domain located over the active site. Lid protects the active site and hence responsible for catalytic activity. In pure aqueous media the lid is predominantly closed, whereas in the presence of a hydrophobic layer it is partially opened. Hence, the lid controls the enzyme activity. In the present review, we have classified lipases into different groups based on the structure of lid domains. It has been observed that thermostable lipases contain larger lid domains with two or more helices, whereas mesophilic lipases tend to have smaller lids in the form of a loop or a helix. Recent developments in lipase engineering addressing the lid regions are critically reviewed here. After on the dramatic changes in substrate selectivity, activity and thermostability have been reported. Furthermore, improved computational models now can rationalize these observations by relating it to the mobility of the lid domain. In this contribution, we summarized and critically evaluated the most recent developments in experimental and computational research on lipase lids.

/pdf/the-lid-domain-in-lipases-structural-and-functional-2a1q417hu6.pdf

The Lid Domain in Lipases: Structural and Functional Determinant of Enzymatic Properties

A new lipolytic enzyme (Lipase III), which specifically hydrolyzed p-nitrophenyl laurate (p-NPL), was found in the culture broth of Penicillium cyclopium Ml. The enzyme was purified with an overall yield of 27% and crystallized by the addition of ammonium sulfate. The crystalline preparation gave a single band on polyacrylamide gel electrophoresis. The molecular weight of the enzyme was about 110, 000 by gel nitration. The enzyme consists of two subunits identical in molecular weight (54, 000), which was estimated by SDS-gel electorophoresis. The optimum pH and temperature for hydrolysis of p-NPL were 6.0 and 40°C, respectively. The enzyme released glycerol from olive oil more rapidly than lipases from Chromobacterium and Pseudomonas. The enzyme also rapidly hydrolyzed triglycerides in serum in the presence of surface active agents. A linear relationship was found between the absorbance at 555 nm and the amount of triglycerides in serum, when it was assayed by using lipase III, glycerol kinase, and α-glycerophosphate oxidase.

Crystallization and Characterization of Lipase from Penicillium cyclopium

Thin-film polyamine biosensor: substrate specificity and application to fish freshness determination

Production of catalase by fungi growing at low pH and high temperature.

A new lipase from Penicillium camembertii U-150, which is specific for monoacylglycerols and diacylglycerols, but not triacylglycerols, was purified as four active components using concanavalin-A–Sepharose column chromatography, crystallized in the form of needles, and its properties investigated. No significant difference was observed in substrate specificity, but molecular mass and other enzymatic properties, such as pH, heat stability and optimum pH and temperature, were clearly different between the unadsorbed and the three adsorbed components on concanavalinA–Sepharose; the three adsorbed components were similar to each other and more stable than the unadsorbed component. On the other hand, after enzymatic removal of carbohydrates from the three adsorbed components, their enzymatic properties became similar to those of the unadsorbed component. The carbohydrates of this lipase contribute to the stability of the enzyme, but not to its enzyme activity. The amino acid compositions of the four components did not differ from each other, and tryptic mapping of the deglycosylated components and amino acid composition of the tryptic fragments were identical. The carbohydrate compositions of four intact components were, however, different from each other. All four components have the same polypeptide backbone and multiple forms of this lipase are due to the differences in composition of the carbohydrates bound in this lipase.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1992.tb19851.x

Kimiyasu Isobe

Papers

Crystallization and Characterization of Lipase from Penicillium cyclopium

Thin-film polyamine biosensor: substrate specificity and application to fish freshness determination

Production of catalase by fungi growing at low pH and high temperature.

Crystallization and characterization of monoacylglycerol and diacylglycerol lipase from Penicillium camembertii.

Purification and some properties of cholesterol oxidase stable in detergents from γ-proteobacterium Y-134