When enzymes were first discovered in the early 20th century, there was a great

Question

When enzymes were first discovered in the early 20th century, there was a great deal of controversy regarding their composition: Were they proteins? Nucleic acids? Carbohydrates? In 1926 a biochemist named James Summer apparently resolved this controversy by crystallizing the enzyme unease (which hydrolyzes urea to ammonia and bicarbonate) from jack beans. He analyzed these crystals by every technique available to him and concluded that they contained only amino acids. Hence, unease (and, by implication, all other enzymes) were proteins.

Explanation / Answer

The actual question is not in the last sentence.

This enzyme is a hexameric protein and has an atomic mass of about 600 000 Da (g/mol) It contains 2 Ni (II) ions (molar mass 58.7g/mol) per each subunit. It means about 700 g Ni in 600 000 g protein or a ratio w/w 1: 860.

To have an “intensely red precipitate’ , let say about 0.1 g complex (or 0.02 g Ni) from 100 mL solution, this solution have to contain the hydrolysate of 0.02x870 g = 18 g (or 18% w/w concentration, that is not usual ) The reaction is made in ammonia buffer (pH=9) . pH is important for the solubility of peptides.

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