Nicotinoprotein (NAD+ -containing) alcohol dehydrogenase: structural relationships and functional interpretations

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Alcohol dehydrogenase (ADH) enzymes are crucial in metabolism.
• Nicotinoprotein ADHs represent a distinct class with unique structural and functional properties.
• Understanding the structure of ADH from Amycolatopsis methanolica provides insights into enzyme evolution and coenzyme binding.

Purpose of the Study:

• To determine the primary structure of nicotinoprotein alcohol dehydrogenase (ADH) from Amycolatopsis methanolica.
• To model the determined structure against known ADH structures and evaluate coenzyme binding.
• To elucidate the phylogenetic position and coenzyme interaction mechanisms of this nicotinoprotein ADH.

Main Methods:

• Primary structure determination of nicotinoprotein ADH.
• Comparative structural modeling against known alcohol dehydrogenase (ADH) structures.
• Analysis of coenzyme binding sites and interactions.

Main Results:

• The nicotinoprotein ADH was identified as a medium-chain dehydrogenase/reductase.
• Structural similarity was found with human class Ibeta ADH, with notable differences in seven loops.
• Phylogenetic analysis places this ADH intermediate between dimeric and tetrameric ADH families.
• Specific loop variations (Thr271Arg, Asn288 insertion) suggest altered coenzyme adenine ring orientation and enhanced hydrogen bonding, favoring stronger coenzyme binding.

Conclusions:

• Nicotinoprotein ADH from Amycolatopsis methanolica exhibits structural features of medium-chain dehydrogenases/reductases.
• Loop differences significantly influence coenzyme binding, suggesting a common binding mode with variations across nicotinoproteins.
• The study enhances understanding of ADH diversity and the structural basis of coenzyme interaction.