Photo: Zinc, by Alchemist-hp (talk) (www.pse-mendejew.de), FAL, via Wikimedia Commons.
A street interviewer asking strangers, “What do you know about zinc?” it is likely to have bewildering aspects and few quick answers. One respondent might recall hearing that zinc pills help reduce the severity of colds. It could be said to be an element, or a metal. Another may have seen zinc supplements in nutrition stores. Well, here’s a new article describing a previously unknown zinc conveyor, which offers an indication and an opportunity to learn more. Also, I’m really enjoying biologist Michael Denton’s latest book, The Miracle of Man. And as it turns out, zinc is a perfect example of a variety of topics in the book.
Zinc is the 30th element of the periodic table and the most abundant metal in the body after iron. However, we weigh only about three grams of zinc. This amount of trace should not be underestimated: it is vital for 10 percent of the proteins and enzymes in our cells. In his previous book The Miracle of the Cell (2020), Denton devoted two pages to zinc, listing the varieties of about 300 enzymes that depend on their unique properties. Last year, in an article on metals in proteins, Casey Luskin mentioned several important functions performed by zinc enzymes.
An important zinc enzyme that Denton focuses on is carbonic anhydrase. It converts the CO2 in our cells into bicarbonate and then reverses the reaction in the lungs. As a result, the end product of oxidative metabolism, carbon dioxide, is safely exhaled into the air for plants to absorb. And that’s not all:
Carbonic anhydrase also helps regulate fluid and pH balance and is involved in the production of essential stomach acid. The enzyme also plays a role in vision. When defective, fluid can build up and cause glaucoma. The enzyme is one of the fastest known, catalyzing up to one million reactions per second. [Emphasis added.]
Clearly, we could not live without these three grams of zinc. But how does such an ideal metal enter the food chain?
Obtaining zinc from the bark in the soil
First, it must be available in the rock of the crust. Zinc is not uncommon, but one kilogram of rock on average contains only 70 milligrams of zinc (JLab Science Education), degrading it to the 23rd most abundant element in the crust (USGS). Hydrothermal vents and volcanoes carry zinc to the surface most often as sphalerite (Geology.com), a compound with iron and sulfur, which is mined around the world. Although zinc has many applications for industry, our interest here is how it is made available to living things. Sphalerite has cleavage planes and a relatively low hardness that make it easy to fragment, but it would never reach the roots of plants without the help of the amazing water cycle of the Earth.
In Chapter 2 of The Miracle of Man, Denton talks eloquently about the hydrological cycle. It lists some of the unique properties of water that make essential minerals bioavailable. These include the ability of water to exist in three states (gas, liquid, solid) at atmospheric temperatures, its low viscosity, its reputation as an almost universal solvent, and its high surface tension. Because of these properties, water seeps into every crack in the rock and breaks it as it freezes. Rivers carry dissolved minerals to the earth, and glaciers crush the fine powdered bedrock. This constant spraying and transport of zinc brought to the surface by plate tectonics and volcanism is the beginning of the element’s journey to the plants, but the work is not done.
Were it not for the soils, with mineral-rich sands and clays that can store water, the minerals would not yet be available for life. Denton sees a “wonderful synergy” of properties independent of water and the earth’s crust that indicate the planet’s “prior fitness” for complex life. He organizes these factors into a “teleological hierarchy” with design implications that suggest providence, not from theological arguments, but from scientific evidence itself. It is a “surprising set” of factors that “presents itself as a monumental testimony that nature is truly adjusted to terrestrial life.”
Getting zinc from the soil to the cell
The “zinc cycle” continues with zinc transported by water to the soil. Clay minerals, Denton points out, have a surface area a thousand times larger than sand. Due to their layered structure and electrical charges, clays attract water molecules and can retain them much longer, challenging gravity that would drain the soil quickly. The roots of plants that penetrate the sands and clays of the soil, however, depend on microbes capable of taking minerals such as zinc and delivering them to the hairs of the root.
An article in Frontiers in Soil Science explains how zinc solubilizing bacteria (ZSB) increase the bioavailability of dissolved zinc ions in the hairs of the root by adjusting the pH. This “benign work of microbes in the ecological cycle of nutrients” again shows the association of “amazing bacteria” with higher organisms.
The precise effect of Zn mobilization that causes ZSB is the deposition of organic acids (OA), which acidify the soil environment and solubilize Zn due to the drop in pH. Other mechanisms include the secretion of chelating agents, such as siderophores, which are thought to play a critical role in iron (Fe), Zn, and the solubilization of other micronutrients.
Getting cell-to-leaf zinc
Plants need zinc for photosynthesis and other essential operations. Getting zinc from root to leaf is a study in itself. A review article in the NIH’s Plants magazine provides a brief overview:
Zn is an essential micronutrient for plant growth and development that is involved in various processes, such as acting as a cofactor for hundreds of enzymes, chlorophyll biosynthesis, gene expression, signal transduction, and plant defense systems. plants … The Zn efficiency of the plant involves the absorption, transport and use of Zn; Plants with high Zn efficiency show high yield and significant growth with low Zn supply and offer a promising and sustainable solution for the production of many crops such as rice, beans, wheat, soybeans and corn. The aim of this review is to report on current knowledge about the key features of Zn efficiency, including root system uptake, Zn transporters, and Zn utilization.
Below, the paper explains how “In the process of absorption, Zn2 + ions travel through the epidermis of the root, the cortex, the endoderm, the pericycle and the xylem and then move to the stem. , leaves, phloem and seeds “. The details are too complicated for our current purposes here, but they can arouse admiration for how many players and processes are involved in getting zinc on the leaf.
Getting leaf zinc to humans
Herbivores and carnivores benefit from the zinc in the leaves, fruits and seeds of plants. Harvard’s nutrition source says “the amount of zinc in our body” is a major player in DNA creation, cell growth, protein building, healing damaged tissue and supporting a the immune system “. And when the sperm meets the egg, zinc makes a fireworks show!
Good vegetable sources of zinc include legumes, whole grains, and nuts. Meat, poultry and seafood are rich sources of zinc. Although zinc deficiency is rare in developed countries, it can cause loss of smell and taste, diarrhea, and other problems. Excess zinc can also be unhealthy, but the body normally regulates zinc homeostasis, keeping the optimum three grams.
This finally brings us to the news: an article last month in Cell by Weiss et al. announced: “Zn 1-regulated GTPase metalloprotein activator modulates vertebrate zinc homeostasis.” The prevention of zinc deficiency or overdose is regulated by a newly identified family of metalloproteins, called ZNG1, which goes into action in situations of zinc starvation.
Using biochemical, structural, genetic, and pharmacological approaches across evolutionarily divergent models, including zebrafish and mice, we demonstrate a critical role of ZNG1 proteins in the regulation of Zn cell homeostasis. Collectively, these data reveal the existence of a family of Zn metallochaperones and assign ZNG1 an important role for Zn intracellular trafficking.
In the accompanying news from Vanderbilt University, Erik Skaar says that “This is the first protein identified that puts zinc in other proteins” and an essential chaperone to respond to zinc deficiency.
We believe that when the body is hungry for zinc, ZNG1 ensures that zinc is delivered to the most important zinc-containing proteins, “said Skaar.” This opens up an exciting new area of biology, where we have these regulatory factors that control a series of different physiological processes by inserting metals “.
From the human back to meaning
This brief adventure in the zinc cycle once again illustrates that the closer you look at intelligently designed biological systems, the more complex you will find. In The Miracle of the Cell, Michael Denton zoomed in on the “pre-fitness” of elements and molecules for their role in complex life. In The Miracle of Man, it approaches the previous physical state of the planet as a whole, with its wonderful cycles, which work together to give man a suitable habitat for the development of technology.
In this new book, Denton advocates a return to an older, human-centered view of the universe that was taken for granted until the Middle Ages, but which was gradually lost when Copernicus, Vesali, and ultimately, Darwin seemed to degrade man of any meaning in the grand scheme for simple cosmic accidents into an indifferent cosmos. Some may find this return to old ideas outrageous, Denton admits. But “Although my conclusions are controversial, the evidence on which they are based is not at all,” he says, just before I go into chapter after chapter of …