Arthur Kornberg (born 1918), American biochemist and Nobel laureate. Kornberg specialised in the study of enzymes, isolating thousands over several decades. He discovered two coenzymes, flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NAD), two important intermediaries in biological oxidations and reductions. Kornberg was awarded the Nobel prize for medicine, with Severo Ochoa, for the discovery of deoxyribonucleic acid (DNA) polymerase I, the enzyme that catalyses the synthesis of DNA from nucleotide building blocks. He also demonstrated that DNA polymerase I could work in a test tube, a process now widely used in biotechnology.