Catalyzes the aminotransferase reaction from putrescine to 2-oxoglutarate, leading to glutamate and 4-aminobutanal, which spontaneously cyclizes to form 1-pyrroline (PubMed:12617754, PubMed:3510672). This is the first step in one of two pathways for putrescine degradation, where putrescine is converted into 4-aminobutanoate (gamma-aminobutyrate or GABA) via 4-aminobutanal, which allows E.coli to grow on putrescine as the sole nitrogen source (PubMed:3510672, PubMed:22636776). Also functions as a cadaverine transaminase in a a L-lysine degradation pathway to succinate that proceeds via cadaverine, glutarate and L-2-hydroxyglutarate (PubMed:12617754, PubMed:30498244). Is also able to transaminate spermidine, in lower extent, but not ornithine. Alpha-ketobutyrate and pyruvate can also act as amino acceptors, although much less efficiently (PubMed:12617754). 2-oxoglutarate + an alkane-alpha,omega-diamine = an omega-aminoaldehyde + L-glutamate 2-oxoglutarate + putrescine = 1-pyrroline + H2O + L-glutamate 2-oxoglutarate + cadaverine = 5-aminopentanal + L-glutamate Optimum pH is 7.2 (PubMed:3510672). Optimum pH is 9.0. Active at alkaline pH. Optimum temperature is 60 degrees Celsius. Highly active from 20 to 80 degrees Celsius. Amine and polyamine degradation; putrescine degradation; 4-aminobutanal from putrescine (transaminase route): step 1/1. Amino-acid degradation. Homodimer. Up-regulated under nitrogen starvation conditions. Expression is sigma-54-dependent (PubMed:12617754). Up-regulated by putrescine; this gene expression regulation is controlled by at least two sigma factors: rpoS under excess nitrogen conditions and rpoN under nitrogen-starvation conditions (PubMed:24906570). Cells lacking this gene show a high decrease in putrescine aminotransferase activity, but are still able to grow with putrescine as the sole nitrogen source. However, a mutant lacking both patA and either puuA, puuB or puuC cannot grow with putrescine as the sole nitrogen source. Can be used in the industrial production of the value-added compound 5-aminovalerate. Belongs to the class-III pyridoxal-phosphate-dependent aminotransferase family. Putrescine aminotransferase subfamily.