Question

Which of these is a non-protein enzyme?
A. α-amylase
B. Nitrogenase
C. Histidine kinase
D. Ribozyme

Answer 1

Hint: We all know that RNA, besides acting as a genetic material helps in catalyzing various metabolic reactions too. This provides base for the fact that enzymes can be non- proteinaceous too.

Complete answer:
Ribozymes are the catalytic RNA (rRNA or Ribosomal RNA) discovered by Sydney Altman and Thomas Cech in the 1980s. They demonstrated that an RNA called Ribonuclease P cleaves the precursor tRNA to form functional tRNA. This RNA or the Ribozymes are the non-protein enzymes.
They are present in mitochondria, nucleus, the chloroplast of eukaryotic animals, and in some viruses as well. They occur naturally in the Ribosomes as peptidyl transferase enzymes on 23S subunit of rRNA and help in forming a peptide bond between amino acids during translation. It plays a vital role in RNA splicing, transfers RNA biosynthesis, and viral replication. They act as ‘molecular scissors' and cleave the precursor RNA and also ligate two molecules of RNA. The ribozymes bear all the features present in a proteinaceous enzyme such as transition stage stabilization, specificity, and Michaeles Menton’s constant.

So, the correct answer is ‘Ribozyme'.

Note:
> Altman and Thomas Cech were awarded the Nobel Prize in 1989 for the discovery of Ribozymes.
> Some of the naturally occurring Ribozymes are peptidyl transferase 23S rRNA, ribonuclease P, hairpin ribozyme, hammerhead ribozyme, GIR1 branching ribozyme, group I and group II introns, HDV ribozyme, etc. They can be modified to produce synthetic ribozymes.
> All kinds of Ribozymes need elements like potassium and magnesium for their functioning.