Insights into the Mechanism of Action of Hyaluronate Lyase

Abstract

Hyaluronate lyases (HLs) cleave hyaluronan and certain other chondroitin/chondroitin sulfates. Although native HL from Streptococcus agalactiae is composed of four domains, it finally stabilizes after autocatalytic conversion as a 92-kDa enzyme composed of the N-terminal spacer, middle ␣-, and C-terminal domains. These three domains are independent folding/unfolding units of the enzyme. Comparative structural and functional studies using the enzyme and its various fragments/domains suggest a relatively insignificant role of the N-terminal spacer domain in the 92-kDa enzyme. Functional studies demonstrate that the ␣-domain is the catalytic domain. However, independently it has a maximum of only about 10% of the activity of the 92-kDa enzyme, whereas its complex with the C-terminal domain in vitro shows a significant enhancement (about 6-fold) in the activity. It has been previously proposed that the C-terminal domain modulates the enzymatic activity of HLs. In addition, one of the possible roles for calcium ions was suggested to induce conformational changes in the enzyme loops, making HL more suitable for catalysis. However, we observed that calcium ions do not interact with the enzyme, and its role actually is in modulating the hyaluronan conformation and not in the functional regulation of enzyme.

Catalytic Mechanism of Hyaluronate Lyase from Spectrococcus pneumonia: Quantum Mechanical/Molecular Mechanical and Density Functional Theory Studies

“…In fact, in the gas phase proton affinity calculations, we built an interesting model in which the calcium ion replaces asparagine and positive histidine residues. The function of calcium ion to modulate the catalytic activity of HLs or other lyases has been discussed extensively. , However, the reason for this is not well-known. In this work, as shown in Table , compared with the inclusion of Hsp, nearly another 100 kcal/mol reduction of PA for C5 atom can be observed to result in PA = 272.6 kcal/mol.…”

“…The function of calcium ion to modulate the catalytic activity of HLs or other lyases has been discussed extensively. 58,59 However, the reason for this is not well-known. In this work, as shown in Table 1, compared with the inclusion of Hsp, nearly another 100 kcal/mol reduction of PA for C5 atom can be observed to result in PA = 272.6 kcal/ mol.…”