Enzyme From Wheat Germ Extends DNA Chains Without a Template

Brodniewicz-Proba and Buchowicz, publishing in The Biochemical Journal in 1980, describe an enzyme purified from dry wheat germ that can add deoxyribonucleotides — the building blocks of DNA — onto existing DNA chains without needing a matching template strand to copy.

This is a biochemistry study, done entirely in the test tube using purified plant material, not cells, animals or humans. The researchers isolated a soluble protein of about 500,000 daltons that splits into two smaller pieces (67,000 and 45,000 daltons) when denatured. It could use short or long polydeoxyribonucleotide chains as a starting point, and worked efficiently — 234 nanomoles of product per hour per milligram of purified protein — even when only one of the four possible nucleotide building blocks was supplied. Using intact double-stranded DNA and a radioactively labeled nucleotide, the enzyme added roughly 40 extra units onto the end of the chain.

The authors note this plant enzyme behaves much like a well-known enzyme from mammalian thymus tissue that performs the same template-free addition, but with key differences: it prefers double-stranded over single-stranded DNA as a starting point, and needs both magnesium and manganese ions to work best. The study does not examine any role in intact plants, health, or disease — it is purely an enzymology characterization.