# Effects of Microgravity, Hypergravity, and Ionizing Radiation on the Enzymatic Activity of Proteinase K

## TL;DR

This study explores how space-like conditions affect the activity of the enzyme proteinase K, finding that it remains functional and sometimes even more active under microgravity and hypergravity.

## Contribution

The novelty lies in evaluating proteinase K's enzymatic activity under simulated space conditions, including microgravity, hypergravity, and ionizing radiation.

## Key findings

- Proteinase K showed enhanced activity after 96 hours under simulated microgravity.
- Hypergravity increased activity at low enzyme concentrations but reduced it at higher concentrations.
- Gamma radiation caused a dose-dependent decline in proteinase K activity.

## Abstract

Space conditions offer new insights into fundamental biological and molecular mechanisms. The study aimed to evaluate the enzymatic activity of proteinase K (PK) under extreme conditions relevant to space environments: simulated microgravity, hypergravity, and gamma radiation. PK activity was tested using azocasein (AZO) as a chromogenic substrate, with enzymatic reactions monitored spectrophotometrically at 450 nm. A rotating wall vessel (RWV) simulated microgravity, centrifugation at 1000× g (3303 rpm) generated hypergravity, and gamma radiation exposure used cesium-137 as the ionizing source. PK activity showed no remarkable changes under microgravity after 16 or 48 h; however, higher absorbance values after 96 h indicated enhanced AZO proteolysis compared to 1 g (Earth gravity) controls. In hypergravity, low PK concentrations exhibited slightly increased activity, while higher concentrations led to reduced activity. Meanwhile, gamma radiation caused a dose-dependent decline in PK activity; samples exposed to deep-space equivalent doses showed reduced substrate degradation. PK retained enzymatic activity under all tested conditions, though the type and duration of stress modulated its efficiency. The results suggest that enzyme-based systems may remain functional during space missions and, in some cases, exhibit enhanced activity. Nevertheless, their behavior must be evaluated in a context-dependent manner. These findings may be significant to advance biotechnology, diagnostics, and the development of enzyme systems for space applications.