Substitution of acidic residues near the catalytic Glu131 leads to human HYAL1 activity at neutral pH via charge-charge interactions.

Human hyaluronidase 1 (HYAL1) and PH20 play vital roles in degrading hyaluronic acids through the substrate-assisted double displacement mechanism. While HYAL1, a lysosomal enzyme, functions optimally under acidic conditions, PH20, a sperm surface hyaluronidase, displays a broader pH range, from acidic to neutral. Our objective was to extend HYAL1's pH range towards neutral pH by introducing repulsive charge-charge interactions involving the catalytic Glu131, increasing its pKa as the proton donor.

Tyr76 is essential for the cold adaptation of a class II glutaredoxin 4 with a heat-labile structure from the Arctic bacterium Sphingomonas sp.

Glutaredoxins (Grxs) are small proteins that share a well-conserved thioredoxin (Trx)-fold and participate in many biological processes. This study examined the cold adaptation mechanism of a Fe-S cluster binding class II Grx4 (SpGrx4) from the psychrophilic Arctic bacterium Sphingomonas sp. PAMC 26621.