Vitamin B3 may have originally come from space, arrived via meteorites

Long before the Iron age smelters learned to extract usable metal from oxidized terrestrial ores, native metallic iron was chipped raw from meteorites and cold-worked into tools. The mother load of meteoric iron was a 100,000 kg care package that fragmented over Cape York, Greenland some 10,000 years ago. A windfall for the Inuit, these caches may have kickstarted a much larger industry. Tantalizingly, a dagger made from similar nickel-enriched iron has even been found in King Tut’s tomb.

But panspermic iron may not be the only thing that meteors gifted. Several researchers now think that in much the same way as iron, vitamin B3 could have been supplied at a critical point in the evolution of life. In 2001, Arizona State University researchers first found vitamin B3 and related molecules in the Tagish Lake meteorite. Last year, Karen Smith and her team at the Goddard Astrobiology Laboratory analyzed eight different meteorites and found that they contained up to 600 parts-per-billion of vitamin B3. They also simulated interstellar conditions in the lab and suggested that the radiation powering various chemical reactions in cloud nebulae could have produced vitamin B3 on ice grains.

Karen and her group recently reported that they were able to synthesize nicotinic and quinolinic acid in so-called irradiated astrophysical ice analogs. These two acids are critical components of the biosynthetic pathway for synthesis of nicotinamide adenine dinucleotide (NAD), one of the most ancient and important molecules of life.

What does this have to with vitamin B3 you might ask? Vitamin B3, or niacin, is readily intraconvertible with nicotinamide. There are many different ways that various forms of life can acquire or produce niacin, nicotinamide, and NAD. Humans can forge niacin in their liver from the amino acid tryptophan, but it is not very efficient. Some estimates suggest it may take 60 g of tryptophan just to produce a gram of niacin. Unless you can get niacin from your diet, you wont have much tryptophan left over to make important goodies like the neurotransmitter serotonin.

In the same way that the Inuit may have been theoretically able to locate rare iron ore and smelt it for knives and fish hooks, a fortuitous meteoric source can get things going a lot quicker. For life, having a ready made exogenous source of niacin family molecules on tap may have been a critical boost before enzymatic pathways were available to catalyze their synthesis.

As we have seen with potentially panspermic molecules like chiral glycine, separating terrestrial and extraterrestrial sources can be difficult. However, pursuit of the fountainhead of life’s critical molecules continues to be one of the most rewarding sources of explanations for many of life’s critical features.