Reconsidering anion inhibitors in the general context of drug design studies of modulators of activity of the classical enzyme carbonic anhydrase

Inorganic anions inhibit the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) generally by coordinating to the active site metal ion. Cyanate was reported as a non-coordinating CA inhibitor but those erroneous results were subsequently corrected by another group. We review the anion CA inhibitors (CAIs) in the more general context of drug design studies and the discovery of a large number of inhibitor classes and inhibition mechanisms, including zinc binders (sulphonamides and isosteres, dithiocabamates and isosteres, thiols, selenols, benzoxaboroles, ninhydrins, etc.); inhibitors anchoring to the zinc-coordinated water molecule (phenols, polyamines, sulfocoumarins, thioxocoumarins, catechols); CAIs occluding the entrance to the active site (coumarins and derivatives, lacosamide), as well as compounds that bind outside the active site. All these new chemotypes integrated with a general procedure for obtaining isoform-selective compounds (the tail approach) has resulted, through the guidance of rigorous X-ray crystallography experiments, in the development of highly selective CAIs for all human CA isoforms with many pharmacological applications.     

1H NMR conformational study of sulfated and non-sulfated cholecystokinin fragment CCK27–33: Influence of the sulfate group on the peptide folding

¹H NMR study of cholecystokinin fragment (CCK_27–33) in (C²H₃)₂SO and in ²H₂O at different pH shows that sulfated (CCK₇) and non sulfated (NS-CCK₇) peptides are under preferentially folded conformations characterized by a β-turn including the sequence Gly-Trp-Met-Asp with a H-bond between the CO of Gly and the NH of Asp. This structure is probably stabilized by an ionic interaction between Tyr and Asp. Moreover, the N-terminal part of CCK₇ forms a C₇ structure with a weak H-bond between the CO of Gly and the NH of Trp. In this model all CCK₇ hydrophobic side chains are in close vicinity, far from the hydrophilic sulfate group. Full interaction with brain CCK₈ receptors could require both the sulfate group and the maintening of conformational constraints.     

Development and fine structure of the bony scutes in Corydoras arcuatus (Siluriformes,callichthyidae)

The development and the structure of the bony scutes have been studied in a growth series of the armored catfish Corydoras arcuatus using light and electron microscopy. Fibroblast-like cell condensations appear in the dermis, in the posterior region of the caudal peduncle, and these will constitute the scute papillae. Collagen bundles of the preexisting dermis colonized by the papilla cells are remodeled and incorporated in the papilla to form, in addition to newly synthesized woven-fibered bony material, the initium of the scute. This process of formation differs from that described for the dermal papilla of an elasmoid scale. During growth, the osteoblasts surrounding the scute constitute the scute sac in which the scute grows. Parallel-fibered bone is deposited on both sides of the initium, and osteoblasts are incorporated within the scute matrix. The remodeling and incorporation of collagen bundles of the preexisting dermis is maintained during growth only in the deep, anterior region of the scute. The posterior region and the upper surface of the scute are close to the epidermal-dermal boundary. When growth slows down in the upper part of the scute, a characteristic, well-mineralized tissue, composed of thin vertical fibrils and granules and devoid of typical striated collagen fibrils, is deposited on the scute surface. A new term, hyaloine, is introduced for this nonosseous, highly mineralized layer constituting the upper part of the scute. Hyaloine shows thin electron-dense lines, which probably correspond to periodic growth arrests. The structure and localization of the hyaloine are compared to other well-mineralized, similar tissues found on the surface of the dermal skeleton in lower vertebrates. © 1993 Wiley-Liss, Inc.     

Use of anion exchange perfusion chromatography for protease recovery at process scale

Summary A protease fromAspergillus niger LCF 8 was purified in anion exchange mode using BioCAD Workstations and the process scaled up. The use of POROS 50 HQ media brings the benefits of Perfusion chromatography i.e. high resolution and high dynamic capacity with very short cycle times. Results obtained at pilot scale enable to purify at process scale 151g of protease/m³ crude broth in 1h. The small column size needed (2.25 l media/m³ crude broth) and the high processing speed of POROS^* 50 HQ compared with conventional media lead to greatly improved cost effectiveness and higher product recovery.