In this study, the physicochemical properties of an enzyme-activated biological solvent for carbon capture were experimentally measured. The solvent consists of an amino acid (l-lysine) mixed with carbonic anhydrase, a composition inspired from human respiration. Densities and viscosities of aqueous blends of carbonic anhydrase enzyme and l-lysine solutions have been measured using an Anton Paar DMA 4100 (capillary type) density meter and a Paar AMV 200 (rolling ball type) viscometer at atmospheric conditions, for a variety of temperatures (303.15–343.15 K) and solution concentrations. The results were compared to various conventional solvents used for carbon dioxide capture, which includes monoethanolamine (MEA), N-methyldiethanolamine (MDEA), and 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4). The studied solvent has a slightly higher density than MEA and MDEA but is lower than BMIMBF4. In addition to that, our solvent has a slightly higher viscosity than MEA but lower than that of MDEA. This offers comparable performance in terms of mass transfer rates in the absorber, pumping costs, and heat transfer. The results were modeled by a semiempirical equation. The model can predict densities and viscosities for a range of solvent concentrations of l-lysine and carbonic anhydrase with high accuracy (AAD% of 0.06% for density and 2.86% for viscosity) and can satisfactorily predict density and viscosity values at other parametric conditions.