Question

Rubisco is an enzyme for
A) Regeneration of RuBP
B) Photolysis of water
C) Carbon dioxide fixation
D) All of the above

Answer 1

Hint: ’RuBisco’ is the short form of Ribulose-1, 5-bisphosphate carboxylase-oxygenase enzyme. It is the enzyme which is used for the carbon fixation process. ‘Rubisco’ is the richest enzyme on earth. It converts atmospheric carbon dioxide into glucose.

Complete answer: The term ‘Rubisco’ was coined by David Eisenberg in 1979. The Rubisco enzyme is involved in the carbon dioxide fixation from the atmosphere and converts carbon dioxide into glucose by plants and photosynthetic organisms. The ‘Rubisco’ enzyme consists of two protein chains known as the large chain (L-chain about 55000 Daltons) and a small chain (S-chain about 13000 Daltons). The large chain is made by chloroplast DNA in plants. ‘Rubisco’ is used in the Calvin Cycle in the fixation of carbon. In the Calvin cycle, Rubisco attacks the carbon dioxide at the carbon number 2 of RuBP and creates a cleavage between carbon 2 and carbon 3, and makes molecules of glycerate-3-phosphate. The various steps followed by ‘Rubisco’ enzymes are embolization, carboxylation, hydration, C-C bond cleavage and protonation. ‘Rubisco’ plays a role as a transcription factor of protein in plants due to abundance. Rubisco used RuBP as a substrate.
Hence, the correct answer is option C.

Note: Magnesium ions are required for ‘Rubisco’ enzyme activity. ‘Rubisco’ is a primary factor in plants for conversion of atmospheric carbon dioxide into glucose by plants. The ‘Rubisco’ does not play any role in the photolysis process. It is the most abundant plant protein.