Carbonic anhydrases (CAs, EC 4.2.1.1) are widely distributed metalloenzymes in both prokaryotes and eukaryotes. They efficiently catalyze the reversible hydration of carbon dioxide to bicarbonate and H + ions and play a crucial role in regulating many physiological processes. CAs are wellstudied drug target for various disorders such as glaucoma, epilepsy, sleep apnea, and high altitude sickness. In the past decades, a large category of diverse families of CA inhibitors (CAIs) have been developed and many of them showed effective inhibition toward specific isoforms, and effectiveness in pathological conditions in preclinical and clinical settings. The discovery of isoform-selective CAIs in the last decade led to diminished side effects associated with off-target isoforms inhibition. The many new classes of such compounds will be discussed in the review, together with strategies for their development. Pharmacological advances of the newly emerged CAIs in diseases not usually associated with CA inhibition (neuropathic pain, arthritis, cerebral ischemia, and cancer) will also be discussed.

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Neurodegenerative diseases are the diseases of the central nervous system with various aetiology and symptoms. Dementia, Alzheimer's disease (AD), Parkinson's disease (PD) and autism are some examples of neurodegenerative diseases. Hyperhomocysteinemia (Hhcy) is considered to be an independent risk factor for numerous pathological conditions under neurodegenerative diseases. Along with genetic factors that are the prime cause of homocysteine (Hcy) imbalance, the nutritional and hormonal factors are also contributing to high Hcy levels in the body. Numerous clinical and epidemiological data confirm the direct correlation of Hcy levels in the body and generation of different types of central nervous system disorders, cardiovascular diseases, cancer and others. Till now, it is difficult to say whether homocysteine is the cause of the disease or whether it is one of the impacts of the diseases. However, Hhcy is a surrogate marker of vitamin B deficiency and is a neurotoxic agent. This Mini Review will give an overview of how far research has gone into understanding the homocysteine imbalance with prognostic, causative and preventive measures in treating neurodegenerative diseases.Over the last 45 years, the term 'hyperhomocysteinemia (Hhcy)' makes its own space in the medical dictionary. It was initiated with the research of McCully in 1969 who suggested that metabolic effects of increased concentration of homocysteine (Hcy) or a derivative of Hcy could be a cause of arterial damage in both homocystinuria and defects in the cblC gene in vitamin B12 [1]. After long years of research, scientists have arrived at the point that 4.4-10.8 lmol of Hcy per litre of blood is the normal range and any range higher than this will be considered a risk factor for human health [2]. A study by Lindenbaum showed that a high level of Hcy is not just the cause of arterial damage but also a marker of vitamin B12 deficiency in patients with neuropsychiatric disorder [3,4]. Till now, it is not very clear whether the elevated level of Hcy in the body causes neurodegenerative diseases or whether the level of Hcy elevated due to initiation and progression of neurodegenerative diseases. In this Mini Review, we will try to focus on the research outcome for both of the aspects till now. Metabolism of HomocysteineMethionine is a proteinogenic amino acid entering the body through the dietary proteins and is used to synthesize other important proteins in the body. It also acts as a precursor of Hcy. Both methionine and Hcy work in combination to maintain the levels of several proteins in the body. To fulfill the need of Hcy in the body, methionine is converted to S-adenosyl methionine (SAM) through activation by ATP. SAM acts as a major methyl donor in the cell, and after donating the methyl group, it is converted to S-adenosyl homocysteine (SAH), which is hydrolysed to Hcy [5]. The two main pathways, remethylation and trans-sulphuration, balance the level of methionine and Hcy in the body ( fig. 1). Remethylation is the process of adju...

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