DNA polymerase I was discovered by
In 1956 Arthur Kornberg at Washington University isolated enzymatic activity from E. coli extracts that incorporated labeled dNTPs into DNA requiring primer, template, and Mg2+. This activity now called DNA polymerase I provided first biochemical proof of enzymatic DNA synthesis in vitro. Kornberg received 1959 Nobel Prize in Physiology for this discovery. His son Thomas Kornberg later discovered Pol III replicase. Original assay using incorporation of 14C thymine and defined activated DNA template-primer paved way for subsequent discovery of replication fork proteins mechanisms and regulation.
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Historical: Discovery of DNA polymerase I by Arthur Kornberg, 1956