Covalent immobilization of enzymes on solid supports provides an alternative approach to homogeneous biocatalysis by adding benefits of simple enzyme removal, improved stability, and adaptability to automation and high-throughput applications. Nevertheless, immobilized (IM) enzymes generally suffer from reduced activities compared to their soluble counterparts. The nature and hydrophobicity of the supporting material surface can introduce enzyme conformational change, spatial confinement, and limited substrate accessibility, all of which will result in the immobilized enzyme activity loss. In this work, we demonstrate through kinetic studies that flexible polyethylene glycol (PEG) moieties modifying the surface of magnetic beads improve the activ-ity of covalently-immobilized DNA replication enzymes. PEG-modified immobilized enzymes were utilized in library construction for Illumina next-generation sequencing (NGS) increasing the read coverage across AT-rich regions.