Search

Meeting the nutritional demand for high‐risk infants is challenging and problems such as necrotizing enterocolitis, growth faltering, and neurodevelopmental impairment persist inneonatal intensive care. The use of pasteurized donor human milk is increasing for high‐risk infants particularly when mother’s milk is insufficient, or breastfeeding is not possible. Proteins are a major source of nutrients in milk and are degraded into peptides and subsequently into nutritious amino acids by proteases. Proteomics studies have identified at least 38 different proteases in human milk, but little research has been performed to biochemically characterize these enzymes. We utilized our mass spectrometry-based peptide digestion assay to detect and characterize the active proteases in human milk. We first acidified the milk to

In agriculture, plants are constantly attacked by pests and disease, thus threatening food security, and increasing the chemical input of pesticides and fungicides meant to maximize crop yields. Analyses of the effects phosphorylation has on asparaginase enzymatic activity have suggested that phosphorylation promotes asparaginase activity (Ahmadian, N., 2020), increasing catabolism of asparagine to release nitrogen in support of the resource-intense immune response. To elucidate whether there is a correlation between asparaginase phosphorylation and enhanced plant immune response, we developed stable transgenic lines expressing phosphomimetic and phosphoabolishing variants of asparaginase. When these plants were inoculated with the fungal pathogen Botrytis cinerea, a decrease in disease resistance was observed in the phosphoabolishing line. This decreased resistance indicates that asparaginase phosphorylation is needed to facilitate plant immune response. As a future testable hypothesis, we speculate that amino acid levels of ammonium and aspartate are affected by asparaginase phosphorylation and subsequently its enzymatic activity. Together this work created and initiated characterization of genetic resources to better develop our understanding of how primary metabolism and nitrogen availability affect plant immunity.

In plants, the precise regulation of cell survival or cell death decisions control effective immunity to different types of pathogens. Cellular damage in plants results in the enzymatic and non-enzymatic peroxidation of fatty acids known as oxylipins. Enzymatic oxylipin biosynthesis often begins with the lipase-based cleavage of linoleic (18:2) or linolenic acid (18:3) from membrane bound lipids. Fatty acids are then dioxygenated by lipoxygenases (LOXs) with regiospecificity at carbons 9 (9-LOX) or 13 (13-LOX) resulting in unstable fatty acid hydroperoxides. Specific oxylipins serve as direct antimicrobial defenses and plant signaling molecules regulating diverse processes such as development, stress acclimation and innate immune responses against pests and pathogens. A commonly studied enzymatic pathway for the 13-LOX 18:3 fatty acid product, termed 13(S)-hydroperoxylinolenic acid, is the sequential activity of 13-allene oxide synthase (13-AOS) and 13-allene oxide cyclase (13-AOC) to yield 12,13(S)- epoxylinolenic acid and finally the 18-carbon cyclopentenone termed 12-oxo-phytodienoic acid (12-OPDA). 12-OPDA is an essential precursor to the 12-carbon cyclopentanone termed jasmonic acid (JA), an essential precursor to the plant hormone JA-isoleucine that controls defense activation and reproduction. In maize (Zea mays) leaves, southern leaf blight (SLB; Cochliobolus heterostrophus) infection results in the additional accumulation of jasmonate-like postional isomers derived from the activity of 9-LOX. These molecules include 10-oxo-11-phytodienoic acid (10-OPDA) and 10-oxo-11-phytoenoic acid (10-OPEA), derived from 18:3 and 18:2 respectively, and the respective series of 14- and 12- carbon metabolites termed death acids (DA). The accumulation of 10-OPEA becomes wound-inducible in fungal-infected maize tissues, is phytotoxic and acts as a direct defense suppressing fungal growth [1]. Conceptually DAs are predicted to be derived from 9-LOX, 9-AOS and novel 9-AOC enzym