Recent studies have focused on tailoring the catalytic currents of multicopper oxidase (MCO) enzymes-based biocathodes to enhance oxygen reduction. Biocathodes modified with natural substrates specific for MCO enzymes demonstrated drastic improvement for oxygen reduction. Performance of 1- pyrenebutanoic acid, succinimidyl ester (PBSE) and 2,5- dimethyl-1-phenyl-1H-pyrrole-3-carbaldehyde (Di-Carb) oriented bilirubin oxidase (BOx) modified gas diffusion biocathode has been drastically improved by incorporating, a porphyrin precursor as electron transfer moiety. Porphyrin precursor modified electrodes demonstrated direct electron transfer reaction of BOx exhibiting larger O₂ reduction current density in phosphate buffer solution (pH 7.0) without the need of a mediator. A remarkable improvement in the catalytic currents with 2.5 fold increase was achieved compared to non-modified oriented BOx electrodes. Moreover, a mediator-less and compartment-less Glucose/O₂ biofuel cell based on direct electron transfer (DET) type bioelectrocatalysis via the BOx-cathode and the glucose dehydrogenase (GDH)-anode demonstrated peak power densities of 1mW/cm² at pH 7.0 with 100mM glucose/10mM NAD fuel. The maximum current density of 1.6mA/cm² and the maximum power density of 0.4mW/cm² were achieved at 300mV with non modified BOx cathode, while 3.5mA/cm² and 1.1mW/cm² of current and power density was achieved with porphyrin precursor modified cathode. The performance improved 2.4 times which attributes to the porphyrin precursor acting as a natural substrate and activator for BOx activity enhancement.