Malonyl CoA reductase (malonate semialdehyde-forming)

Malonyl CoA reductase (malonate semialdehyde-forming), also known as malonyl-CoA reductase (MCR), is an enzyme belonging to the oxidoreductase family. It catalyzes the NADPH-dependent reduction of malonyl-CoA to malonate semialdehyde. This reaction is a key step in certain metabolic pathways, specifically those involved in the utilization or synthesis of β-alanine and related compounds.

The enzyme’s systematic name is malonate-semialdehyde:NADP+ oxidoreductase (CoA-acylating). The reaction it catalyzes can be represented as follows:

malonyl-CoA + NADPH + H⁺ ⇌ malonate semialdehyde + CoA + NADP⁺

Malonyl CoA reductase plays a crucial role in microorganisms where it functions within a pathway enabling the assimilation of β-alanine as a source of carbon or nitrogen. The malonate semialdehyde produced is then typically further processed by other enzymes, such as malonate-semialdehyde dehydrogenase, leading to acetyl-CoA and entry into the central metabolic pathways.

The precise mechanism of action of malonyl CoA reductase involves the transfer of hydride from NADPH to malonyl-CoA, resulting in the formation of the semialdehyde and the release of coenzyme A. Different isoforms of MCR may exist in various organisms, potentially with variations in their substrate specificities or regulatory mechanisms. Further research is needed to fully elucidate the structural and functional characteristics of MCR enzymes across different species and their precise roles in various metabolic contexts.