Insights into the Mn2+ Binding Site in the Agmatinase-Like Protein (ALP): A Critical Enzyme for the Regulation of Agmatine Levels in Mammals

Abstract

Agmatine is a neurotransmitter with anticonvulsant, anti-neurotoxic and antidepressant-like effects, in addition it has hypoglycemic actions. Agmatine is converted to putrescine and urea by agmatinase (AGM) and by an agmatinase-like protein (ALP), a new type of enzyme which is present in human and rodent brain tissues. Recombinant rat brain ALP is the only mammalian protein that exhibits significant agmatinase activity in vitro and generates putrescine under in vivo conditions. ALP, despite differing in amino acid sequence from all members of the ureohydrolase family, is strictly dependent on Mn2+ for catalytic activity. However, the Mn2+ ligands have not yet been identified due to the lack of structural information coupled with the low sequence identity that ALPs display with known ureohydrolases. In this work, we generated a structural model of the Mn2+ binding site of the ALP and we propose new putative Mn2+ ligands. Then, we cloned and expressed a sequence of 210 amino acids, here called the “central-ALP”, which include the putative ligands of Mn2+. The results suggest that the central-ALP is catalytically active, as agmatinase, with an unaltered Km for agmatine and a decreased kcat. Similar to wild-type ALP, central-ALP is activated by Mn2+ with a similar affinity. Besides, a simple mutant D217A, a double mutant E288A/K290A, and a triple mutant N213A/Q215A/D217A of these putative Mn2+ ligands result on the loss of ALP agmatinase activity. Our results indicate that the central-ALP contains the active site for agmatine hydrolysis, as well as that the residues identified are relevant for the ALP catalysis.

Manganese‐Induced Highly Fluorescent Oligodopamine for Sensitive Detection of Dopamine Neurotransmitter by Catalytic Action of H2O2/MnO2 Nanosheets

“…[66][67][68] Manganese-induced complex has a coordinated structure in which four hydroxyl (from two catechol) groups and two amine groups are linked to the Mn 2þ center (Figure S6, Supporting Information). [69,70] Eventually, the catalytic H 2 O 2 /MnO 2 system produced the highly fluorescent F-ODA coordinated with the central Mn 2þ ion, so-called Mn 2þ @F-ODA. The size of Mn 2þ @F-ODA complex was estimated as 1084 AE 219 nm that is larger than that of F-ODA (363 AE 60 nm) (Figure S7, Supporting Information).…”

Trace Elements in Alzheimer’s Disease and Dementia: The Current State of Knowledge

“…It is also a cofactor of several enzymes. There are a few Mn-dependent enzymes, like arginase, agmatinase and glutamine synthetase, that take part in neurotransmitter synthesis [116].…”

Hollow Mesoporous MnO2 Nanospheres as Light Source-Free Carriers for Synergistic Starvation and Chemiexcited Photodynamic Tumor Therapy

“…Due to the characteristics of consuming ROS, GSH has become an important factor to reduce the cytotoxicity of ROS and the therapeutic effect of cancer. − To address this problem, it is necessary to find ways to reduce GSH at the tumor site while using ROS to treat cancer. Manganese dioxide (MnO 2 ) nanomaterial as a GSH-consuming drug has attracted extensive attention. − In addition, manganese is an important trace element in the organism and can be excreted by the liver, which reduces the long-term toxicity of manganese dioxide drugs and increases their biological safety. − MnO 2 remains stable in neutral and alkaline environments and is gradually broken down in acidic environments, which ensures that manganese dioxide-based drugs are not broken down before reaching the lesion . Improving the hypoxic environment of tumors requires not only “increased income” but also “decreased expenditure”.…”