Evolutionary "Time Travel": Human Protein Modification Pathway Traced Back to the First Cellular Organisms

New research reveals the human N-glycosylation pathway is an ancient process dating back to the first cellular organisms, shedding light on the evolution of the ER.

By: AXL Media

Published: Mar 26, 2026, 4:57 AM EDT

Source: Information for this report was sourced from Higher Education Press and the journal Engineering.

Decoding the Ancient Language of Glycans

Glycosylation—the enzymatic attachment of sugar chains (glycans) to proteins and lipids—is one of the most fundamental processes in human biology, governing everything from immune recognition to cell signaling. Despite its ubiquity, the evolutionary "birth" of this machinery has long remained a mystery. New research published in the journal Engineering by a team from the University of Zagreb and the Ruđer Bošković Institute has finally mapped this timeline. Using a technique called phylostratigraphy, they traced the "genetic age" of human glycosylation machinery (GM) genes, finding that the core of our cellular "sugar-coating" system was established billions of years ago, at the very dawn of cellular life.

The Binary Origin of the Endoplasmic Reticulum

The study’s most striking discovery involves the spatial organization of the N-glycosylation (NG) pathway within the endoplasmic reticulum (ER). The researchers found a clear evolutionary "split" in the ER’s architecture: the genes responsible for glycan synthesis on the cytoplasmic (outer) side of the ER membrane date back to the origin of all cellular organisms (prokaryotic origin). Conversely, the genes operating within the lumen (inner cavity) of the ER emerged much later, during the origin of eukaryotes. This binary distribution provides strong evidence for a long-standing biological hypothesis: that the complex internal membranes of human cells evolved through the inward folding, or invagination, of an ancestral prokaryotic cell membrane.

A Genetic Census of 503 Organisms

To build this evolutionary map, the team analyzed 503 different organisms representing the major branches of the tree of life. By utilizing the blastp algorithm and cross-referencing data from the Kyoto Encyclopedia of Genes and Genomes (KEGG), they assigned human GM genes to 29 distinct "phylostrata" or age levels. The census revealed that 56% of our glycosylation genes are ancient survivors from the first cellular organisms, while another 24% represent the massive burst of innovation that occurred during the transition to complex eukaryotic cells. This suggests that while the "engine" of glycosylation is primitive, the "steering" and "refining" mechanisms are distinctly eukaryotic.