Human Spermidine Synthase

Updated: 2026-07-25

Overview

Thermospermine synthase (ACL5) is an aminopropyltransferase enzyme critical for synthesizing thermospermine, a tetraamine regulating plant vascular development and stress responses. It is encoded by the ACL5 gene in Arabidopsis and homologs in other species. Unlike spermine synthase, it exhibits unique substrate specificity for decarboxylated S-adenosylmethionine (dcSAM). First identified in Arabidopsis thaliana, this enzyme plays a pivotal role in xylem differentiation and stem elongation. Its dysfunction leads to dwarf phenotypes, making it a target for agricultural biotechnology aimed at improving crop architecture and resilience.

Physical and Chemical Properties

Thermospermine synthase typically exists as a homodimer with a molecular weight of 50-60 kDa per subunit, depending on the organism. It requires Mg²⁺ as a cofactor and operates optimally at pH 7.5-8.0 in vitro. The enzyme is stable at 4°C for short-term storage but degrades rapidly at temperatures above 37°C. Its activity is measured spectrophotometrically by monitoring putrescine consumption or thermospermine production via HPLC. Commercial preparations often include stabilizing agents like glycerol (10-20%) to preserve activity during storage and shipping.

Main Applications

In plant research, thermospermine synthase is studied to understand its role in lignin deposition and tracheary element formation. Genetic modulation of ACL5 expression has shown promise in engineering crops with improved stem strength and drought tolerance. Biotech applications include CRISPR-based editing of ACL5 homologs to develop dwarf rootstocks for orchards or ornamental plants. The enzyme is also used in vitro to produce thermospermine for biochemical assays and as a standard in polyamine quantification studies.

Safety and Storage

As a non-hazardous biological material, thermospermine synthase requires standard biosafety level 1 (BSL-1) handling. Use gloves and eye protection to prevent irritation from buffer components. Spills should be cleaned with 70% ethanol. For long-term stability, lyophilized enzyme should be stored at -20°C in moisture-proof containers. Reconstituted solutions retain activity for 1-2 weeks at 4°C when supplemented with 0.1% BSA or 10% glycerol. Avoid freeze-thaw cycles beyond 2-3 repetitions to prevent activity loss.

B2B Procurement Guide

When sourcing thermospermine synthase, prioritize vendors providing Certificate of Analysis (CoA) with specific activity (≥0.5 U/mg) and endotoxin levels (<1 EU/μg). Recombinant versions (E. coli-expressed) offer higher consistency than plant-extracted forms. Bulk orders (≥10 mg) may qualify for 15-30% discounts. Consider suppliers offering custom formulations (e.g., His-tagged for purification) or species-specific isoforms (e.g., Oryza sativa ACL5). Validate shipments with activity assays upon receipt, as improper cold chain handling is a common cause of product failure.