The input of agrochemicals in the aquatic compartment can results in biochemical injuries for living organisms. In this context, the knowledge of alterations of enzymatic activities due the presence of agriculture pollutants contributes for the elucidation of the mechanisms of toxicity, implementation of economic methods for monitoring purposes and establishment of maximum allowed concentrations. In the present work, the above considerations are discussed, and data concerning changes in enzymatic function by pesticides and fertilizer contaminants are reviewed. Also, we focused on the acid phosphatase due its susceptibility to several pollutants and diversity in cellular functions.

Pseudokirchneriella subcapitata é uma alga verde unicelular amplamente distribuída em corpos d´agua e solos. Devido a sua natureza cosmopolita, seu uso é recomendado por protocolos nacionais e internacionais na realização de estudos de ecotoxicidade. A alteração da atividade de fosfatases por agentes poluentes de origem agrícola, como metais pesados, tem sido largamente usada como um biomarcador na avaliação de risco e biomonitoramento. No presente trabalho foi comparada a extração da fosfatase ácida de P. subcapitata por diferentes métodos e estudada a sua estabilidade, especificidade por substratos, cinética e efeito do Hg2+ no extrato bruto. O congelamento e descongelamento, associado com ultrassom, foi o método que proporcionou maior rendimento de extração. A enzima, praticamente estável por armazenamento a -20ºC, durante aproximadamente seis meses, demonstrou uma atividade ótima em pH 5 e um valor de Km para o p-nitrofenilfostato (pNPP) de 0,27 mM. Alguns substratos naturais foram hidrolisados com uma intensidade semelhante à do substrato sintético pNPP. Diferentemente dos estudos de exposição a curto prazo (24 horas), observou-se inibição da atividade específica nas culturas expostas durante 7 dias, com um valor de CE50 (concentração de Hg2+ que promove 50% de decréscimo da atividade específica) equivalente a 12,63 μM Hg2+.

Pseudokirchneriella subcapitata is a unicellular green algae widely distributed in freshwater and soils. Due to its cosmopolitan characteristic, its use is recommended by national and international protocols in ecotoxicity studies. The alteration of phosphatase activities by agriculture pollutants like heavy metals has been extensively used as a biomarker in risk assessment and biomonitoring. In this study, we compared the extraction of acid phosphatase from P. subcapitata by different procedures and we studied the stability, substrates specificity, kinetics and the effect of Hg2+ in the crude extract. The freezing and thawing technique associated with probe sonication was the most suitable method of extraction. The enzyme was stable when frozen at -20ºC for at least six months, showed an optimum pH of 5 and a Km value of 0.27 mM for p-nitrophenylphosphate (pNPP) as substrate. Some natural organic substrates were cleaved by a similar extent as the synthetic substrate pNPP. Short term exposure (24 hours) to Hg2+ had little effect but inhibition of the specific activity was observed after 7 days with EC50 (concentration of Hg2+ that promotes 50% decrease of specific activity) value of 12.63 μM Hg2+.

Riboflavin, a component of the B2 vitaminic complex, plays important roles in biochemistry, especially in redox reactions, due to the ability to participate in both one- and two-electron transfers as well as acting as a photosensitizer. Accordingly, low intakes of this vitamin have been associated with different diseases, including cancer and cardiovascular diseases. Riboflavin is thought to contribute to oxidative stress through its capacity to produce superoxide but, interestingly, it can also promote the reduction of hydroperoxides. This peculiar and multifunctional behavior allows riboflavin to take part in various biochemical pathways as a nucleophile and an electrophile, turning it into a versatile and important biological compound.

Protein phosphorylation-dephosphorylation catalyzed by the opposing and dynamic action of protein kinases and phosphatases probably, is the most crucial chemical reaction taking place in living organisms. Protein phosphatases are classified according to their substrate specificity and sensitivity to inhibitory or activator agents, into two families of protein phosphatases: serine/threonine phosphatases and tyrosine phosphatases (PTPs). PTPs can be divided into 3 groups: tyrosine specific phosphatases, dual and low molecular weight phosphatases. The role of tyrosine phosphorylation in mitogenic signaling is well documented, and one would predict that vanadate, pervanadate and other oxidant agents (protein tyrosine phosphatase inhibitors) may act as a growth stimulator.