Activation Effects of Carnosine- and Histidine-Containing Dipeptides on Human Carbonic Anhydrases: A Comprehensive Study.

Giulio Vistoli,Giancarlo Aldini,Andrea Angeli,Claudiu T Supuran,Laura Fumagalli,Clelia Dallanoce

doi:10.3390/ijms21051761

Abstract

l-Carnosine (β-Ala-l-His) and several other histidine-containing peptides, including two N-methylated forms on the imidazole ring (l-anserine and l-balenine), two derivatives modified on the carboxyl function (carcinine and l-carnosinamide), two analogues differing in the length of the N-terminal residue (l-homocarnosine and Gly-l-His) and the N-acetyl derivatives, were investigated as activators of four isoforms of the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1). The four human isoforms hCA I, II, VA and IX were activated in the low to high micromolar range, with a rather complex structure activity relationship. A performed computational study allowed us to rationalize these results and to propose a binding mode of these activators within the enzyme active site. Similarly to other CA activators, the here studied peptides could find relevant pharmacological applications such as in the management of CA deficiencies, for therapy memory and enhancing cognition or for artificial tissues engineering.

Highlights

The dipeptide l-carnosine (β-Ala-l-His) represents the prototype of a set of histidine-containing peptides which are found in the entire animal kingdom, where they are primarily expressed in the muscles and are significantly abundant in other excitable tissues [1,2]
Along with this clear and direct mechanism, indirect mechanisms can contribute to the buffering capacity especially when considering that histidine analogues are reported to be potent activators of some isoforms of the human carbonic anhydrases which play a key role in modulating and maintaining the physiological pH [9]: EZn2+OH− + CO2 EZn2+HCO3− +H2O EZn2+OH2 + HCO3−
When considering the rapid hydrolysis that carnosine and some of its derivatives undergo in plasma by serum carnosinase, one may figure out that the buffering capacity has a predominant role in those tissues which synthesize carnosine at mM concentrations [26] while the CA activation can have a relevant role in the other tissues which are reached by low amounts of histidine containing peptides [27]

Summary

Introduction

The dipeptide l-carnosine (β-Ala-l-His) represents the prototype of a set of histidine-containing peptides which are found in the entire animal kingdom, where they are primarily expressed in the muscles and are significantly abundant in other excitable tissues [1,2]. The well-known properties of the imidazole ring render almost all these derivatives metal-chelators, antioxidants and endowed with a significant buffering capacity [5]. Apart from N-acetyl-l-carnosine, these dipeptides are able to inhibit the protein carbonylation by quenching reactive carbonyl species (RCS) through a two-steps mechanism which involves both the primary amine and the imidazole ring and yields a final Michael adduct [6]. The buffering capacity is primarily ascribable to the ionization properties of the imidazole ring which shows a pK value (pK = 6.72) close to the physiological pH [7]. Along with this clear and direct mechanism, indirect mechanisms can contribute to the buffering capacity especially when considering that histidine analogues (such as histamine and histidine itself [8]) are reported to be potent activators of some isoforms of the human carbonic anhydrases (hCAs) which play a key role in modulating and maintaining the physiological pH [9]: EZn2+OH− + CO2 EZn2+HCO3− +H2O EZn2+OH2 + HCO3−

Methods

Results

Discussion

Conclusion